What’s the Deal With Over-Balancing?

Increasing the reciprocating mass above the commonly accepted 50 percent (of measured) rotating mass can be helpful in extreme high-rpm applications—emphasis on the word “can.”

Jon Greenbaum; New Haven, CT: I just bought a 347-cube stroker kit for my 302 Ford. The kit includes a crank, pistons, rods, pins, rings, and bearings. The package came with a balance sheet indicating it has been pre-balanced, and I don’t have to spend the money again for balancing. But my machine shop tells me otherwise. Who is right, the crank company or my machinist? Also, we got talking about over- and under-balancing. It was confusing. What’s the deal?

Steve Magnante: Most of today’s prepackaged stroker kits arrive in a pre-balanced condition. We’ve personally double-checked a few balance cards and found the work is pretty good—within a few grams at worst, versus our observations—but I’m in agreement with your machine shop. What if he takes the word of the “pre-balanced” package and it turns out to be way off? Then, who’s on the hook to make it right when it vibrates at cruising speed, or worse, self-destructs at 6,700 rpm?

Balancing a rotating/reciprocating assembly won’t add much to the total bill, so let them go ahead and double-check the crank-maker’s claims. Everybody will sleep better. As for the over/under-balance concept, let’s remember that balancing seeks to equalize the force generated by the rotating (round-and-round) and reciprocating (up-and-down) components. Since the connecting rods operate in both realms, things get complicated.

When working with a V-type engine with a 90-degree bank angle (all of our classic American V8s fall into this category), the process of balancing includes calculating the bob weight. Bob weights are temporarily attached masses equal to the total weight of two rotating masses and one reciprocating mass. Secured to the crank’s rod journals, they simulate the weight and motion of both the reciprocating and rotating masses as the crank is checked in the balancing machine, and it is here that some engine builders employ the over/under-balancing trick.

In a standard 90-degree V8, the reciprocating weight factor is calculated as being equal to 50 percent of the rotating weight (when assembling the bob weights). But if extremely high rpm levels are expected, inertial forces are naturally increased. Some crankshaft shops theorize that by increasing the reciprocating mass percentage to slightly more than the 50-percent norm—usually 51 or 52 percent—a more accurate bob weight total mass results. The resulting “over-balanced” crankshaft is thought to be better able to absorb the shock of extremely high piston velocity.

The wild card exposed by deviations from the normal bob-weight formula is an inevitable compromise in the quality of the balance (aka an unbalanced condition) at some other point in the rpm range. The only time overbalancing is called for is in extreme racing applications where crank speeds are going to remain at some well-known point, and operation at other rpm points are less important. In the real world of general-purpose street and strip fun machinery, this scenario is simply not encountered. Stick to the generally accepted balancing methods.

Can Cross-Drilled/Slotted Brake Rotors be Resurfaced?

Sam Haunterlover64; via CarCraft@carcraft.com: The left-rear shock-absorber mount on my 1972 El Camino SS broke off the axletube, and I was wondering where I can find a new bracket to weld on. Also, is it possible to surface cross-drilled disc-brake rotors?

Steve Magnante: I’m not aware of any outfits selling individual reproduction shock-absorber mounts to remedy your situation. I’m guessing rust ate away at your mount and there’s not enough left to repair and re-weld to the axletube. But it’s a fact companies like Currie, Drive Train Specialists, Moser, Quick Performance, Strange, and others sell ready-to-install axles that have all the required mounting ears, flanges, and mounts already attached for quick, bolt-in installation.

Knowing that, there’s a strong chance that a call to one of these outfits will result in the sale of the loose, individual mount you’re seeking. When you weld it to the axletube, make certain to match the original axle-to-shock orientation or you’ll introduce a bind that’ll kink the shock and cause trouble. If the axle is out of the car, don’t forget to emulate the original vehicle load and pinion angle when you weld the fresh bracket in place. If the axle is still under the bed of your El Camino, be sure to support the car under each axletube instead of by the frame with the rear suspension hanging down.
Regarding your question about resurfacing cross-drilled (and slotted) disc-brake rotors, the hassle involves the interrupted cut caused by the many drilled holes in the friction surfaces. Cutting tips can be quickly dulled and damaged by the rapid-fire load/unload shocks as the rotor spins in the lathe. The remedy is to take very light cuts of a few thousandths at a time and work up to the cutting depth needed to restore a smooth, flat friction surface. This adds time, especially if the drilled passages are offset on each face of the rotor (versus aligned holes made by a straight-through drilling operation). Offset holes require that one side of the rotor be cut at a time, where aligned holes allow for simultaneous cutting of both faces at once. Adding it all up, in some cases, the price of replacement rotors is less than the man-hours needed for refurbishment. Shop wisely. Also know that in high-volume shops (think Mercedes-Benz dealerships) where drilled rotors are encountered daily, specific resurfacing equipment is used. Instead of the single-point cutting tips used in most brake lathes, these establishments employ fluid-lubricated stones and turn the rotor at much higher speeds to restore freshness. The stones don’t get snagged in the holes like the pointed cutter and the fluid washes away grit that would otherwise flaw the surface finish.

These stone-type disc-brake rotor cutters are becoming more common as drilled and slotted disc-brake rotors grow in popularity. But remember, any time material is removed from a brake rotor, its ability to absorb and dissipate heat is compromised and it is forever less resistant to overheating under severe use. Be sure to check with the disc-brake manufacturer to learn how much material can safely be removed. Any disc with enough warping to be felt through the brake pedal (as a pulsation) has been severely overheated, is badly warped, and usually needs more material removal than is safe. Minor surface abrasions can safely be remedied, but more often than not, you’re best off simply replacing scarred rotors with fresh units.

NASCAR Valvetrain Tricks

David Borkowski; via CarCraft@carcraft.com: NASCAR runs pushrod V8 engines at 9,000 rpm. How do they make the valvetrain live for 500 miles?

Steve Magnante: You raise a good point. Unlike many other forms of endurance racing, which allow overhead-cam (OHC) engine architecture, NASCAR’s insistence on the use of pushrods and rocker arms places special challenges on the valvetrain. In an OHC engine, the relationship between the camshaft lobe and valve stem is direct, reducing the load on the valvesprings. Taking nothing away from Formula 1 or IndyCar engine builders, they don’t face the hassle of controlling the inertia of lifters, pushrods, and rocker arms like NASCAR engine builders do.

The magic behind how they get 358ci, pushrod-equipped V8s to deliver nearly 900 hp and live at 9,500 rpm for 500 miles comes down to metallurgy and harmonics. The wire used to make NASCAR valvesprings is carefully controlled for quality, then specially polished and coated with carbon and titanium nitride to eliminate the same kind of stress risers that can cause connecting rods to fail under load. Every part of the system is also made from the lightest—but strongest—metal available. Titanium valves with dainty stem diameters (as small as 6 mm) and valvespring retainers with scalloped edges and drilled perimeters shed many ounces. Special oil squirters target jets of engine oil against the springs to reduce inter-coil friction and carry away heat.

The engine blocks also play a role in valvetrain survival. The camshaft tunnels have been raised way up away from the spinning crank and enclosed in housings to keep flying oil from dragging on the crank. The raised cam also reduces the span between the lobes and rocker arms. This, in turn, allows for much shorter pushrods. And since the pushrods’ stiffness-to-mass ratio is dependent on overall length, these shorter pushrods reduce the load the valvesprings have to control. The added space inside the crankcase makes room for another group of oil squirters, targeting the pistons and rods.

Harmonics are another area of importance when crankshaft speed hits 9,500 rpm. The advent of modern testing equipment, like the Spin-Tron, exposed a raft of evils caused by high-frequency vibrations. In particular, the classic timing chain proved to be a major source of nasty harmonics leading to valvespring fatigue and failure. Though perfectly safe for daily use and occasional high-rpm spurts, constant operation at 9,000 rpm sets up shivers that run throughout the engine. By switching to a beltdriven cam (with NASCAR’s blessing), valvespring longevity was greatly improved due to the flexible belt’s ability to absorb the harsher notes played at 9K.

There are other tricks, but these are the major ingredients that allow today’s NASCAR engine builders to make the impossible possible. It’s a high-stakes race environment where cost is no object and a typical “bullet” costs $50,000.

Hot Coffin-Nose Cord

Solly Burton; Graysville, IN: I’m writing about my 85-year-old grandpa’s 1937 Cord 812. He bought it 25 years ago in Texas, but really got started rebuilding it eight years ago. He swapped a 1980 Oldsmobile Toronado 350 and FWD unit in the place of the original Lycoming flathead-eight and three-speed manual transaxle. It runs well, but we’ve been fighting an overheating problem for five years. So far we’ve had a bigger custom radiator made, tried numerous electric cooling fans, fan shrouds, coolant-expansion tanks, high-flow water pumps, coolant additives, and various thermostats—including running with no thermostat. Even after all this, it’ll get up to 210 degrees within 20 minutes of a dead-cold start-up. Last spring grandpa broke his hip, but he has already recovered—he’s pretty tough and a fast healer. He really wants to drive this car before he is too old.

Steve Magnante: Solly, give your grandpa a handshake for us for being persistent and not giving up. Before digging in, keep in mind that 212 degrees Fahrenheit isn’t a disastrous number. The happy zone for most gasoline-burning, internal-combustion engines is between 160 and 210 degrees. And in the case of many modern engines, 220 degrees is the norm to help curb exhaust emissions (but they’re designed for it with specific metallurgy, clearances, gaskets, and lubricant). Your 1980 Olds 350 really isn’t too far above the safety zone.
Having said that, you seem to have addressed all the obvious culprits that cause overheating, so it might be time to look at the engine itself. It isn’t unheard of for silt, rust, old gaskets, and other debris to accumulate inside an engine block and reduce the space/volume available for liquid coolant motion. Did you rebuild the Toronado engine or simply swap it over? Also, with the custom radiator you’ve undoubtedly got some non-stock hose routing. Are any hoses pinched or kinked from being installed within close quarters? A kinked hose will render even the best radiator on Earth null and void if coolant isn’t flowing to and from it freely, and don’t discount the fact that suction-side hoses can easily collapse if there is no coiled spring inside to add stiffness. This is a classic cause of engines that idle all day nice and cool but boil over at highway speed—when water-pump activity increases and sucks the return-side hose shut. Be sure the return-side hose is rigid and reinforced from within. Heck, why not replace any spans of straight hose more than 5 inches long with stainless-steel tubing of the correct diameter. That’ll rule out “collapsed veins.”

Beyond the hoses, look into your engine’s air/fuel mixture and ignition timing. An overly lean mixture under load can lead to overheating, as can retarded ignition timing. Make sure each item is within factory specs or is in the acceptable range for your application. Judging by the description, your grandpa’s Cord represents a sweet blend of stock and custom elements. The Cord 812 was only made in 1937 and was an outgrowth of the 1936 Cord 810. Company founder Errett Loban Cord only produced 2,830 810 and 812 Cords in 1936–1937, all of them right up the road from you in Auburn and Connersville, Indiana.

Hats off to grandpa for choosing a set of chromed 1966 Toronado rims. The wheels that came on the 1980 Toronado donor car were painted black, had different shapes, and were meant to be hidden under fake wire wheel covers (optional) or bland standard stainless hats. By contrast, the 1966 Toro rollers were deliberately designed by Oldsmobile to emulate the look of the original two-piece chromed wheel covers used by Cord. With their massive amount of inboard (negative) offset, they were designed to accommodate the extra width of the Toronado’s FWD system. Beyond that, GM research of the 1960s solved the vibration problem that haunted most previous FWD designs, regardless of origin. By placing the steering knuckle outside of the tire-tread centerline, rather than inside, and using double-jointed axleshafts, the resulting “outward pivot axis” forced wheel designers to go all the way with negative offset to keep the tires within the body shell.

When George Hurst and “Gentleman” Joe Schubeck created the Hurst Hairy Olds in 1966 (a 442 exhibition match racer with twin-Toronado powerplants driving both sets of tires), they retained the stock Toronado wheels! Yes, they looked great, but none of the aftermarket custom wheel makers—least of all Hurst—had an off-the-shelf mag that fit!

The post Car Craft Ask Anything: Answers to Your Burning Questions appeared first on Hot Rod Network.

“The customer called and said his 440 Six Pack engine was making noises and was very down on power,” said Donnie Wood, proprietor of R.A.D. Auto Machine in Ludlow, Massachusetts, a New England hot bed of muscle car engine rebuilding and dyno testing. “Over the phone,” said Donnie, “it can be almost impossible to diagnose the cause of unusual sounds and poor performance.” He asked the customer, “why don’t you bring it in?”

And so two weeks later, a forlorn looking 440 Six Pack engine arrived at the R.A.D. loading dock. Grimy and rusty, it was a long way from its factory-rated 390 horsepower and 490 lb-ft of torque. After digging in, it was determined this was a case of an owner who was in way over his head. When the valve covers were removed, a set of high-zoot roller rockers appeared, but upon close inspection, several lash adjustment balls were scarred and pitted from improper clearance and oil starvation. Beyond that, the exotic rockers were squandered on a mild hydraulic flat-tappet camshaft—not a solid-lifter unit where their adjustability would actually be needed.

“Grimy and rusty, it was a long way from its factory-rated 390 horsepower and 490 lb-ft of torque.”

But when Donnie examined the trio of Holley 2300 series carburetors, he knew they hadn’t been running correctly for years. Sticking vacuum diaphragms, incorrectly routed vacuum hoses, and loose fuel deposits foiled their ability to function as designed.

After taking stock of the situation, Donnie asked the customer what he really wanted the engine to do. The response was: “I just want to cruise around in my Road Runner and burn rubber once in a while. Plus, I don’t want to touch the engine.” With zero desire to manage the adjustable valve gear, the customer was OK with taking a few steps backwards. After all, an exotic engine that isn’t running right is no better than a stock engine that’s running properly.

“I just want to cruise around in my Road Runner and burn rubber once in a while. Plus, I don’t want to touch the engine.”—(every) Six-Pack owner

The customer did have one demand: the Six Pack had to stay. It seemed he loved the visual impact of showing off the macho triple carbs at car shows. And who could blame him? Simplifying things with a return to a single four-barrel carburetor was strictly off the table.

While the factory Six Pack setups of 1969-1/2 to 1972 (yes, a handful were released in ’72) were calibrated for great street and strip performance, the Six Pack seems to be one of those induction setups that attracts well intentioned tinkerers. But often, these “wizards” do more harm than good. The truth is, unless a stroker crank or radical camshaft enters the picture, the factory calibrations are nearly impossible to improve on if street cruising and occasional lead footing is the goal.

“…the factory calibrations are nearly impossible to improve on if street cruising and occasional lead footing is the goal.”

Let’s watch as the R.A.D. Auto Machine team revives a sickly Six Pack that churns out 418.6 horsepower at 4,900 rpm and 492.3 lb-ft at 2,800 rpm on premium unleaded pump gas.

The post Restore Your 440 Six Pack Better Than New! Dyno Proof Too! appeared first on Hot Rod Network.

When it comes to engines, finely balancing the rotating assembly is a step that is often overlooked. This is a shame because it can add smoothness, performance, and longevity to any engine. In this installment of our Barton 528 Street Hemi build, we’ll be doing just that.

First, we need to express the importance of proper engine balance. Internal engine balancing—as opposed to external balancing—effectively adds performance and longevity, along with reduced wear, noise, and vibration. Other benefits are an engine that will run smoother with less vibration which creates less havoc on the main and rod bearings while also helping the other parts to last longer.

All crankshafts are balanced at the factory, but not to the same degree as needed for a racing engine or high-performance street engine—which usually means holding the imbalance to less than ¼ ounce-inches. The factory balance is adequate for production vehicles that don’t see regular high-rpm blasts. Inside the internal combustion engine, the crankshaft must rotate at high speed. As the rotational and reciprocating parts increase speed, vibration gets worse. In fact, vibration gets worse as a function of the square of its rpm. As an example, at 8,000 rpm, second-order vibrations are four times as bad as at 4,000, not twice as bad.

If we look at the kinematics of a rotating assembly a little closer, we can see why balancing plays such an important role. If we assume the crankshaft is rotating at a constant speed, when the crank throw is halfway between top dead center and bottom dead center, the wrist pin is actually more than half way down its travel. On the return trip, when the crank throw is half way between bottom dead center and top dead center, the wrist pin is not even half way up the bore. All this means the piston spends more time at the bottom of the bore than the top of the bore, and travels faster at the top than it does the bottom, and that’s a major contribution to vibration.

Lucky for us, on a cross-plane V8 crank like the kind found in most domestic V8 engines including all Mopars, the variation in piston speed is offset. As a piston accelerates as it nears TDC on one cylinder, it’s always being compensated for by another piston that is decelerating as it nears BDC. But this sets up a secondary vibration in the “y” plane, where the engine see-saws front to back, and puts stress on bearings that goes up exponentially as rpm increases. It’s for this reason that internal balancing will always be better for high-rpm high-performance street and race engines.

To solve this, crankshaft counterweights are designed to offset balance the inertial effect from the weight of the piston and connecting rod moving in both rotational and reciprocating motions (up and down) at speed. Most V8 engines use large counterweights towards the front and rear of the crankshaft. Those larger front and rear counterweights are strategically placed further away from the crank’s centerline for a better balance effect. A custom billet crank goes one step further and places counterweights in the interior to further smooth out vibration.

Another source of second-order vibration that has particularly significant consequences for bearings is crankshaft torsional dynamics. If all cylinders are presumed to fire with the same downward force on their pistons, the amount of twist imparted to the crank throw will vary depending on the distance from the flywheel. At full power, the front cylinder may, as an example, cause a 2-degree deflection in the position of the rod journal while the rear cylinder may deflect only a half degree. Having a good crank such as our Hemi’s Molnar unit can therefore reduce vibration while improving bearing life.

One last fun fact to contemplate about balancing is that the amount of vibration an engine produces is proportional to the power, but inversely proportional to the mass of the non-reciprocating, non-rotating components. How the mass of non-moving parts is distributed around the moving parts also comes into play, as this affects the engine’s overall polar moment of inertia. Since many racing engines have lightweight alloy blocks, this makes them particularly sensitive to balance issues.

You may have also heard of the term “over balance” in reference to race engines. Typically, the crankshaft is considered 100 percent rotating mass; the piston, rings, locks, and wrist pin as 100 percent reciprocating mass; and the rod as half reciprocating and half rotating mass. When bob weights are calculated for balancing, the rod is weighed at both ends, and the masses of all components (along with bearings, locks, and an approximation for the mass of the oil) are plugged into a formula that assumes the center of mass for the connecting rod is at its center. At typical street rpm, this isn’t an issue, but on competition engines that regularly see operation over 9,000 rpm, the balancing formula needs to compensate for the connecting rod’s center of mass being closer to the big end. As a result, many engine builders will over-balance an engine by two or three percent to reduce vibration and extend bearing life.

On an externally balanced crankshaft for a street engine, there is extra offset weight added to the front harmonic balancer and rear flywheel, torque converter, or flex-plate. When balancing an externally balanced crankshaft, those previously mentioned components need to be installed on the crankshaft for balancing. On an internally balanced crankshaft like ours, it’s not necessary.

OEM engines like the LA 360, B-400, and the ’74-78 RB 440 use an externally balanced cast crankshaft from the factory. One commonly overlooked vibration issue we’ve seen is forgetting to account for external balance when upgrading to a high-stall torque converter on an externally balanced engine—which are typically zero-balanced for internally balanced engines. In this case, the externally balanced engine needs to use a balanced flex plate (available from B&M or A&A) designed for an externally balanced engine to prevent the vibration issue. Also, the stickshift folks need a balanced flywheel made for use with the externally balanced cast crankshaft. Forged crankshafts are internally balanced and can use zero-balance components that attach to the front and rear of the crankshaft.

In case you missed the first two stories of our Barton-built 528 Street Series Hemi crate engine, here’s the lowdown. In the first installment, Barton helped us rework the latest edition of the Street Hemi cylinder head, Edelbrock’s Victor Jr. [http://www.hotrod.com/articles/port-edelbrocks-hemi-head-38-cfm/] These latest castings received input in design and development updates from Ray Barton himself—a world renowned Hemi expert. For the second story, we showed the special machine work that goes into a Barton-blueprinted Hemi block [http://www.hotrod.com/articles/behind-curtain-ray-barton-hemi-machine-shop-secrets/]. Barton’s machining magic will aid in extra power and durability—something everyone wants. All balancing at Ray Barton Racing Engines gets done in-house on every Hemi they build.

Above – The wrist pin, rings, and piston pin locks are also weighed individually to assure they all weigh the same for each cylinder. Their weight is added to the reciprocating weight equation to help calculate the bobweight needed for balancing.

The post Add Power, Smoothness, and Longevity With Balancing! appeared first on Hot Rod Network.

Modern-day electronic fuel injection has been simplified to the point where it oftentimes makes little sense not to be running it. However, some are still spooked by the implied complication of the system, specifically the fuel supply.

Fortunately, all of those complicated aspects have been simplified with such offerings as carburetor retrofit throttle bodies and returnless (dead-head style, no return line) option in-tank fuel pumps. Along with their latest, the self-learning Sniper EFI system, Holley also offers universal in-tank fuel pump modules for use with existing—not EFI-specific—fuel tanks and cells. In basic terms, that means your average four-barrel–equipped car can be upgraded to EFI without having to swap intake manifolds, fuel tanks, or any other scary things!

If you’re handy with a wrench, a hole saw, tape measure, and a pair of wire crimpers, retrofitting a “pumpless” gas tank to accommodate Holley’s in-tank fuel module kit is a breeze. Available in two sizes—255LPH (for up to 550-cfm EFI/700-cfm carburetor) and 450LPH (for up to 875-cfm EFI/1,100-cfm carburetor)—the 12-130 series retrofit modules feature Holley’s new HydraMat filter, which provides a consistent fuel supply due to its large capacity, pouch-like construction. An anodized aluminum hanger (mounting flange) allows you the ability to easily place the pump in the tank near the sending unit. Each kit comes complete with all the pump-related components, though a 30-amp relay for the pump is also recommended.

Of the entire installation job, dropping/draining the tank and cutting the forthcoming hole may be the only labor-intensive aspects—the rest is as easy as pie … or cutting a hole, measuring and setting the pump depth, and connecting some wiring and fuel lines!

The post Holley’s In-Tank EFI Fuel Pump Install appeared first on Hot Rod Network.

Building a hot rod from the ground up involves decision making and problem solving. Problems will arise whenever you begin to mix and match parts not destined for the original car. A good example would be installing a W-motor (348/409 Chevrolet) in a 1960 Corvette, or any other hot rod. This was Chevrolet’s original big-block motor and it was never available in a production C1 Corvette, although it has been said that a couple of test cars were built by GM at the time, but I digress.

So, the decision is made to put the W-motor in the Corvette and happily the engine fits quite nicely in the engine bay. Coupled to a TCI Automotive 700-R4 transmission it appeared the driveline was going to be a very straight forward engine swap. Hood clearance was an issue but we managed to keep the FAST dual-quad EFI units and reproduction Corvette air breathers below the hood line. We were thrilled with the progress and with the body back on the frame it was time for things like throttle linkage, wiring, and mounting the alternator and A/C compressor. We assumed there would be a simple solution to mounting the engine accessories. There were some scary moments but in the end the solution was simple enough.

First we began with traditional brackets available to mount the alternator and compressor to the front of the motor. These brackets mounted the accessories much too high, causing hood interference. They also placed the alternator and compressor too wide for our application, well outside of the heads. Small beads of sweat are now beginning to form on our furrowed brow. How are we going to get these things mounted?

After spending a couple of days trying to design brackets that might work we realized that Billet Specialties makes a Tru Trac system for the W-motor family. Viewing the assembly online it appeared to be the answer we were desperately seeking. A quick call to the tech people at Billet Specialties confirmed our belief that the Tru Trac would solve our problems, but they asked us to check for two potential problems. One, be certain there is ample room between the lower crank pulley and the crossmember in the car. We checked, plenty of room there, problem one averted. And then the voice on the other end of the line informed us of potential problem number two. “Our Tru Trac system uses the lower front motor mount tappings to mount our brackets. Not all 348/409 motors had these holes drilled and tapped.” More sweat on the brow. A quick trip to the shop and our fears were confirmed, no tapped holes in our motor. Now what?

Within the confines of our engine bay the Tru Trac was our best solution. It mounted the A/C compressor and alternator in front of and below the valve covers. Add perfect pulley alignment, a modern serpentine belt and the simple good looks of black anodized aluminum parts and we were sold on the system. However, to employ the system we would have to drill and tap four holes in the front of a freshly rebuilt engine that was installed in the car. No small chore.

We were fortunate to have ample room in front of the engine. If the motor was out of the car and on an engine stand this would have been quite simple, but at least we could get the required drill in the engine bay, now the problem was precisely locating the holes.

Both the alternator and compressor mounting brackets employ the water pump bolts and the lower motor mount holes as fastening points. That made locating the holes on the block quite simple. After removing the water pump, the brackets were mounted to the front of the block using the water pump mount holes. Then a 7/16-inch transfer punch was used through the lower bracket holes to accurately transfer the location of the new holes. Now came the hard part, drilling the four holes and tapping them for the 7/16-14 thread bolts. Drilling them on center in the proper location was not a problem, but how would I be able to keep the drill level and square to the block? The holes must be perfectly straight. The Billet Specialties brackets are machined to very close tolerances so the bolts and studs must pass through the brackets perfectly straight. I decided to fabricate a simple drill fixture.

The drill fixture was made from a piece of 3/8-flat stock and using the brackets as a template the water pump hole centers were transferred to the plate and drilled for 3/8 holes. Next the Billet Specialties bracket was bolted to the steel plate. Then using a 7/16-inch transfer punch, the lower motor mount holes were located. The bracket was unbolted from the plate and the two lower holes were drilled using a drill press. It was decided the best method to keep the drill square to the engine block was by using two tubular drill guides. To that end two pieces of 1/4×1-1/2-inch steel pipe were cut and tack welded to the plate. Using the drill bit and a machinist square we checked to be certain the drill bit was square, this test must be done every 90 degrees to ensure the drill is straight in all directions. It took a bit of light hammer work to get the two pipe sleeves in the proper position, but once we were satisfied with the drill fixture we bolted it to the water pump studs and began the drilling process.

We purchased a brand-new, size U, made in the USA, drill as we wanted a true hole, the right diameter, done by a drill bit that was up to the task. A cordless Milwaukee drill fit in the confines of the engine bay. Drilling into the block on the passenger side could have resulted in drilling through the block and into the cavity where the fuel pump bolts to the engine. We wanted to avoid any through-holes for fear we would get metal filings inside the engine. The plan was to drill 9/16-inch deep into the block so we measured and marked the drill with a wrap of tape. Just in case we penetrated the block, we placed a magnet inside the fuel pump opening and also packed a clean shop rag in the hole to prevent any unwanted filings from going into the oil pan.

We began drilling the top hole and the new drill handled the cast-iron material easily. We drilled to our depth mark and were pleased that we had not drilled through the block. We moved to the lower hole with the same results, a clean hole that did not go through the block. Now all we needed was threads. Once again we purchased a brand-new, made-in-the-USA tap set that consists of a standard taper, a plug, and a bottom tap. Again we selected high-quality Irwin tools because this was no time to be fooling around with cheap import drills and taps that could easily snap off or dull during use.

A squirt of tapping oil on the tap and in the oil was the first step. Then we began tapping the threads first using the plug tap. This tap has enough taper to easily start the threads. Work slowly and be certain the tap is square in the hole. After the plug tap had started threads we backed it out and used the bottom tap to thread the hole all the way to the bottom. With the holes threaded we test-fit our A/C compressor bracket and found the lower hole was perfect but we could not catch the threads for the upper motor mount hole that uses a recessed Allen bolt. A test with a stud showed the threads were good but we were ever so slightly off center. The solution was to use a fine file and remove a very small amount of material from the outside diameter of the Allen cap bolt head. Presto! It threaded in place and was torqued to 76 lb-ft.

The same process was used on the driver side for the alternator bracket and we are pleased to say we had no through holes and everything lined up and was torqued in place. The hard part was officially over and the remainder of the installation was just pure fun. Every single piece fit perfectly, all the supplied bolts worked as they should, and the black anodized brackets looked fantastic installed. Billet Specialties makes this entire installation easy because of the fully illustrated, clearly written instruction sheet. The new Edelbrock aluminum water pump supplied with the kit will go a long way to ensuring proper cooling.

The final step was bolting the polished Powermaster alternator and A/C compressor in place, followed by installing the serpentine belt. The end result was an alternator and compressor mounted in front and below the valve covers in an extremely compact style. The accessories look very “factory mounted” in this location and we could not be happier with the entire kit. It solved a major problem for us and did it in fine style. Using our method this kit will work on any W-motor. If you are working on a W-motor project we offer two bits of advice. One, if you have an engine without motor mount holes drill and tap the motor mount holes while the block is on an engine stand. Two, plan on using a Tru Trac system in the car, you’ll be glad you did.

The post Installing Billet Specialties Tru Trac System on a 348 Chevrolet Engine appeared first on Hot Rod Network.

Cheap turbos are nothing new. The thrifty, yet potent, snails have been on the market for quite some time. You’ve read about them before, probably seen one at your local dragstrip, and have maybe even pondered buying one. Before you do, HOT ROD brings you the truth, the whole truth, and nothing but the truth about cheap turbo kits.

A few years ago, eBay was the place to go for dollar-store turbochargers. It still is, with plenty of bargain performance parts, but the cheapest turbo kits we found came from another website: Amazon. The kits, sold under the brand Auto Dynasty, come in five tiers based on the amount of pieces included—you know, like ordering fried chicken. The base kit (five-piece) includes the turbocharger, exhaust manifolds, gaskets, wastegate, and some assorted V-band flanges and oil fittings, all for the pocket-friendly price of $539.99 (Amazon Prime members even get free shipping). On the opposite end of the spectrum is the 22-piece kit ($1,049), which includes a plethora of electronic gadgetry: a turbo timer; gauges for temperature, boost, and so on; oil coolers; and a few pieces we really couldn’t tell you what they did.

We bought the big kit, but now know the 10-piece kit is the sweet spot for most hot rodders, as it includes all of the necessary parts, without some of the highly questionable components we suggest avoiding. Basically, you get all of the hot-side/cold-side plumbing, the oil lines for the turbo, an intercooler, a blow-off valve, and a wastegate (in addition to everything in the five-piece kit). In theory, this is all of the parts to build a functional turbo system. The 10-piece kit will set you back an entirely manageable $699. Without a degree in global business economics—is that a thing?—it is truly difficult to comprehend how this much “stuff” costs so little. More so than anything, it brings up the question of, “Do you get what you pay for?”

To resolutely answer that question, we packed up our freshly delivered boxes of Amazon-sourced turbo parts, grabbed a tired, old small-block out of a C10 truck, and drove to Westech Performance to put the rumor of the cheap turbo to the test.

Piecing the Puzzle Together

Steve Brulé, the brains behind Westech’s engine dyno, loves when we bring him boxes of mismatched cheapo parts to assemble in his 100-degree dyno cell. It truly is a credit to his good nature and—um—patience that he lets us come at all. At least the water bubbling in the water-brake dyno’s reserve pool adds to the humidity—a personal sauna of sorts to ease the stress of what all of us thought would be a challenging test.

Before the turbo assembly/torture testing began, we bolted our run-of-the mill, 350ci small-block Chevy up to the dyno. It was given a baseline pull to assess not only its health but its horsepower before boost. The result was good oil pressure, a steady idle, and an output of a whopping 301 hp and 321 lb-ft of torque, via a loaner Holley 950HP carb and open 1.75-inch dyno headers. With a staggering output of 0.85 horsepower per cubic inch, it wouldn’t be breaking any records in NA trim.

Queue the dramatic music: It was time to bolt on the turbo—there are no instructions, by the way. And…problem. Our first move was to install the passenger-side turbo manifold. We almost instantaneously found the No. 8 tube wanting for spark-plug clearance—really, really wanting. We actually couldn’t fit a spark plug in at all, let alone a plug wire, in the allowed space. Out came the torch and several hammers to massage the renegade manifold into compliance.

After about an hour of hammer, heat, repeat, we had the hot side of the kit in place. The crossover tube does require welding. If you aren’t that savvy with a torch, most muffler shops can expand the tubes for a slip fit and exhaust clamp or, if nothing else, double the thickness to weld to.

The next major problem occurred on the cold-side piping. The blow-off valve is mounted on a pipe that sandwiches via two silicone couplers before the carburetor. Well, someone’s tape measure must have broke because the diameter of the blow-off valve mount spec’d in at 2.5 inches while the rest of the system measured 3.5 inches. Rather than create a bottleneck right before the carb, Curtis Mowery, the engine’s owner, opted to simply TIG-weld the valve onto one of the intake pipes. This worked fine, but if you can’t weld aluminum, expect to add this to the tab.

Another sizing issue—no doubt the result of the kit being pieced together from so many manufacturers—came at the air filter, which was too small to slip over the turbo inlet. Either a reducer or a new filter will be required.

After fighting some issues and coming up with the above quick fixes, we finally had the entire kit assembled on the dyno. It was frustrating at times and took some problem solving, but it was far from impossible.

But wait, “The turbo is backward,” you say? Yup, it sure is. No, we aren’t that thick. That’s the only way it would mount. “If you tried to reverse it, the turbo would be exactly where the brake booster/master cylinder is in any car,” said Westech’s Joe Trujillo. We even tried reversing the turbo on the flange, but that caused it to interfere with the valve cover. Even a stock valve cover still hit. While this setup will work on the dyno, in a car, having the exhaust come out the front would be a hurdle to route and would look kind of goofy. Our thought was to weld a spacer to the turbo flange to raise it enough that it would have room to clear the valve cover. So far, we keep taking off points from the turbo kit’s score, but would we be adding them back once the engine fired?

Fuel to the Fire

A turbo kit is just about useless unless you have a way to fuel it. To that end, we pieced together a Holley 650 double pumper converted to blow-through spec. With only less than $50 invested in the carb, it was a mystery whether or not it would be able to keep up with the turbo or provide the correct mixture under boost. Surprisingly, it would turn out to be the most turnkey component of the test.

To duct boost to the engine, Mowery bought a Spectre carb hat for $101.99—again, from Amazon. We used a rubber air-cleaner gasket and O-ring on the air-cleaner stud to seal in the boost. The kit includes a fuel pressure regulator that is vacuum referenced. Short answer: We didn’t trust it. The thing uses tiny hose barbs supposedly capable of supplying 600 hp worth of fuel—we weren’t going to chance it. Running lean under boost is more-often-than-not catastrophic, and it simply wasn’t worth the risk. An Aeromotive regulator took its place and was referenced off a brass fitting we tapped into the carb hat.

The vacuum routing diagram, which feeds the blow-off valve and wastegate could double as a Neolithic cave drawing, but it gets the point across—kind of. The kit also comes with 253.5 feet of vacuum tubing, so shortages shouldn’t be an issue.

We stood back, sweaty and a little frustrated, to admire what was now about four-ish hours of assembly work; bear in mind we were working in the confines of a dyno cell and not in the much tighter parameters of an engine bay—it could be worse.

T-Minus 3… 2… 1… Houston, We Have a Problem

You could practically touch the anxiety in the dyno cell as Brulé lit the engine for the first time. Mowery and I were giddy kids at the back of the classroom waiting for the first pull—Brulé, not so much, with his years of engine-tuning experience subconsciously warning him of the impending oil slick on his pristine dyno cell floor.

Since the ignition timing was already dialed during the earlier pulls, the engine was already good to go. Brulé called up the test program and leaned back on the throttle. It was quiet, far quieter than any dyno I’d ever heard, the turbo and exhaust piping covertly exhaling exhaust gases toward the back of the cell. The calm, however, was only momentary as the turbo spooled and the needle on the SuperFlow readout raced toward 650 lb-ft of torque before Brulé could wing the throttle back closed.

Ecstatic shouts and hollers reverberated around the room. Did we really crack 650 lb-ft at 4,500 rpm on what, only minutes ago, was a tired hunk of iron? We did!

Our excitement was short-lived as Brulé pointed to a graph of boost pressure. Like the slope of Mount Everest, the pressure curve rose rapidly at a daunting angle. It had pegged 17 pounds at 4,500 rpm and was still on a lunar flight path when Brulé aborted the pull. This kit would easily make 20 pounds of boost if someone winged the engine to redline.

As cool as the big number is, it’s downright dangerous. A kit that makes 20 psi of boost out of the box is going to ruin someone’s day—and, worse yet, their engine! Our scenario had everything going right for it: an expert tuner, 116-octane race gas, cold coolant, cold spark plugs, and ignition timing that had already been retarded to 25 degrees. Change any of those variables and any internal-combustion engine could become external real quick!

The Fix

Inarguably, the kit works. The turbo makes boost and the engine makes power. But that’s only half of the equation. Being able to control the turbo, manage the boost level, and create a safe tune-up is paramount. Changes had to be made.

Originally, Brulé and Eric Rhee, Westech’s chassis dyno brains and resident turbo expert, figured the wastegate spring was too stiff, allowing too much boost to build before it opened. The wastegate’s job is to vent exhaust around the turbo, reducing flow to the turbine wheel and allowing the turbo to slow down. The duo tried switching to lighter springs, chopping springs, yelling at the springs, all to no avail. The wastegate still wasn’t doing its job and the boost kept climbing to unsafe levels.

As a last-ditch effort, Brulé made a pull with no wastegate at all. The result was 1 psi of boost; we realized the wastgate wasn’t able to move enough exhaust even when it was open. We pried on it with a screwdriver and realized that, even when it was fully open, the valve was no more than ¼ inch off the seat. The solution was to add a second wastegate on the opposite bank. Trujillo handled the TIG-welding chore and spliced a second Auto Dynasty wastgate into the mix.

The original wastgate springs were reinstalled, and it was time to make yet another dyno pull. To everyone’s relief, the second gate did the job. We could finally manage boost! And for an even tighter element of control, Rhee plumbed an electronic boost controller inline with both gates.

With the boost set at 12 pounds, we wound the motor up one last time. The turbo did as it was told and held the forced air right at the designated mark—12 psi was worth 546 hp and 613 lb-ft of torque. The powerband had a beautiful curve with tons of torque down low and a smooth, graceful climb to peak power. This mill would make for a killer street car!

The Review

At the end of the day, we’ll say this: Cheap turbo kits are not for the faint of heart. They require a seasoned car veteran who can handle elements of basic fabrication, engine tuning, and problem solving.

We were impressed at the power the kit made, but also concerned at the potential for disaster in box-stock form. Massaging this into the confines of a vehicle would be a challenge, but is certainly not impossible.

As for the components, the turbo gets an A+. It had no issues over the two-day test and the clearances still seemed tight after our abuse. Power potential is clearly not an issue with it. The exhaust manifolds get a worse grade (we’d say a D) as spark-plug clearance was not checked, nor was turbo mounting position. They will take massaging at the minimum. The wastegate was the biggest loser, having been clearly inadequate and the main culprit behind what could have been an engine-destroying problem. For that, it earns an F. As for overall fit, finish, and compatibility, we’d have to give the kit a C. About 75 percent of the components play nice with each other, but the variance in tubing size and incorrect air filter prove that quality control is an issue. There were also tons of random hardware bits, fittings, and other stuff that didn’t seem to have a designated use.

Is this the cheapest way to make horsepower? Inarguably. “I remember when you used to have to build engines to go fast,” Brulé chided us. But it’s the truth; bolt one of these on, work out the bugs, and you’re on your way to high-10-second passes—with plenty of reengineering required, of course.

Things You’ll Also Need

The kit doesn’t include a carb hat, so that will be an extra expense. We used this Spectre hat (PN 9849) with good results. It sells for $101.99. Also, a boost-referenced fuel regulator is a must. Without one, boost pressure in the float bowls will slow (potentially even stop) fuel from flowing into them. This Aeromotive unit (PN 13204) can easily handle the task and adds $180.97 to the overall cost. In fairness, the 13-piece Auto Dynasty kit ($799) does include a regulator, but it looked pretty sketchy and utilized small hose barbs as inlet/outlets. Chancing fuel problems wasn’t an option for us.

Sources

Aeromotive
913.647.7300
AeromotiveInc.com

Auto Dynasty (sold through Amazon)
Amazon.com

Holley
866.464.6553
Holley.com

Spectre
909.673.9800
SpectrePerformance.com

Westech Performance Group
951.685.4767
WestechPerformance.com

The post You Can Buy a Small-Block Turbo Kit for $699! But Does it Work? appeared first on Hot Rod Network.

Using Engine Cycle Analysis to monitor the combustion process

A number of years ago, during the early life of this column, we touched on a subject that remains an issue, particularly when building or modifying an engine intended for racing. It was also early in the availability and affordability of in-cylinder combustion pressure testing as a function of incremental crankshaft angles. “Engine cycle analysis” (ECA) had evolved from the academic community and was further explored among the higher-end motorsports, such as F1 and NASCAR. This technology provides combustion pressure measurement in virtually real-time while linking the data to high-resolution crankshaft angles. From these data, a variety of thermodynamic-related calculations give particular insight into how a given engine is converting fuel into heat during the combustion process.

This approach to combustion analysis provides a way to look inside the combustion space, particularly with respect to cyclic dispersion and how frequently it occurs. Let’s take a closer look into what this condition affects.

First, let’s discuss what the term means. We have on multiple occasions discussed the importance of air/fuel charge quality as it pertains to both air flow and fuel atomization efficiency. It’s a frequent topic because the quality of both is critical to optimizing combustion efficiency and power. Further, we’ve suggested a poor man’s way of monitoring combustion efficiency is through the study and optimization of brake-specific fuel consumption (BSFC) data. Not only does ECA enable measure the pressure history from beginning to end of each combustion cycle, it can also measure such history’s cycle to cycle in a running engine. Hang in with us. This’ll all come together soon.

Since in any given cylinder of a running engine, it’s not only possible but also probable that on a cycle-to-cycle basis, the same combustion efficiency level will vary due to all the previous conditions we’ve listed about air and air/fuel charge quality. Combustion cycle to combustion cycle, there can be variations in the actual air/fuel ratio in the spark plug’s gap, again based on the conditions we’ve attempted to describe. Based on the amount of combustion residue (exhaust gas) that remains in the combustion space, turbulence at the beginning of the burn and separated fuel can cause variables in the air/fuel ratio at the gap from cycle to cycle in the same cylinder. Regardless of the cause, it is this cyclic dispersion that results from cycle to cycle changes in combustion efficiency. OK, we’ve now come full circle. We began by noting conditions that can affect combustion efficiency and introduced the fact that it can subsequently impact cycle-to-cycle power levels.

What are additional causes of cyclic dispersion that you must consider and can address? Well, separated air and fuel in the combustion space is pretty high on the priority list. Of course, these two are related. For example, mixture motion (swirl and tumble) has been used in both stock and racing engines, with the possible exception of the racing engines that operate at significantly higher rpm. By definition, swirl motion is air (also with fuel) that is rotating about a vertical axis upon entering the combustion space, while tumble (also with fuel) that is rotating about pretty much a horizontal axis as it meets the combustion space. Taken to excess, it’s possible to generate too much of either (or both), causing fuel to be centrifuged out of its suspension (mechanically separated—and you know the results of that. There can be, and often is, a corresponding reduction in volumetric efficiency. Of course, the consequence from this is reduced torque.

During the period when this column was presenting commentary from a number of noted engine builders, one of the questions consistently asked was about the advantages or disadvantages of EFI in racing, particularly at the local level. That question was included for a reason. We wanted to canvas that particular group of engine builders who were and are in relatively consistent contact with the weekend, or possibly touring, racer. Consensus opinion seemed to favor carburetors instead, for reasons that we don’t need to consider here.

But think about this: The difference in atomization efficiency between EFI and carburetors is significant. And guess what? This leads us back to improvements in cyclic dispersion, whereby the carburetor (remember Smokey’s comment about it being a controlled leak) does a poor job of atomizing fuel, as compared to EFI. While we are not advocating the use of EFI (with its cost and learning curve), the comparison illustrates the benefits from, and importance of, good fuel atomization, especially when using carburetors.

How much power loss can unattended cyclic dispersion cause? We’ve seen a fair amount of data that indicates a range of 5 to 8 percent. Stated another way, if we can reduce the amount of cyclic dispersion and use more of the fuel supplied an engine, you can expect about this amount of power gain, over baseline power that’s experiencing the problem. Bottom line? A reduction in cyclic dispersion tends to improve combustion efficiency while translating to increased crankshaft torque.

Serious students of internal combustion engines say not only does the reduction of cyclic dispersion net more power, but it also helps assure combustion efficiency during the early stages of a given burn, particularly since peak cylinder pressure occurs just past TDC on the power stroke and varies somewhat as a function of revolutions per minute. Initiating a quality burn early in the process helps overall combustion efficiency and power.

To circle back to other discussions about air/fuel charge quality and ways to improve combustion (once again in an attempt to compensate for a carburetor’s poor atomization efficiency), recall that we discussed mechanically aiding the break-up and attending suspension of fuel in the inlet air stream. The texturing of certain areas along the intake path (post carburetor), properly done, can help the overall cylinder-filling event with more combustible air/fuel charges. In fact, some cylinder head modifiers currently employ their own brands of this by the practices they follow themselves. We even recall some favorable results that came from small dimples placed on the backside of intake valve, but that’s an entirely different topic.

We are typically dealing with engines of multiple cylinders, connected in some fashion that allows them to influence the overall volumetric efficiency of the entire package. Understanding the phenomena and seeking ways to minimize their effects can net an increase in power. The use of ECA can produce revealing and useful data. However, it’s possible to watch for and experiment with much less-expensive techniques, which only require fundamental understanding about the telltale signs and for which you can apply comparatively simple tools.

The post Engineology: Engine Cycle Analysis appeared first on Hot Rod Network.

Tested: Total Seal’s 110V Ring Filer

Few processes in assembling an engine are as tedious as filing piston rings. It requires patience and precision, carefully fitting the top and middle rings to each bore. It’s not something for an assembly line. Considering the new ring packages used in modern pistons often include thin but tough steel or ductile iron rings that make old cast iron rings seem soft in comparison, the thought of using our old hand-cranked ring filer gets less and less appealing. That’s where Total Seal’s 110V power ring filer came in.

The filer uses a stationary motor with an abrasive wheel and a table that moves perpendicular to the wheel with an indicator to track the table’s lateral movement. Dialing in travel of the table allows the user to remove measured sections of the ring as the table pivots toward the wheel. We tested it while filing a set of 1/16-inch Mahle rings for a Pontiac 400 stroker.

Total Seal’s power ring filer is the size of a shoebox and is sturdy enough to stay planted on the workbench. One end of the motor holds the grinding wheel; the other is a deburring wheel.

Mahle provides specs for their ring gaps, which vary by the engine’s intended application. Erring on the side of caution we decided to use the specs for a drag racing engine, which called for slightly larger ring gaps than those of a street-only engine. At .0045-inch gap per inch of bore size for the top ring and .005-inch gap for the second ring, our bore size of 4.155 inches meant a gap of .01875-inch for the top and .02077-inch for the bottom. We rounded those up to .019-inch and .021-inch, respectively. Then we wrote them down on the paper-covered workbench.

To know how much to remove from each ring, we first squared each ring in the bore that it would eventually call home. Total Seal’s ring squaring tool makes sure the ring is square in the bore for an accurate measurement. You can use a piston, but the tool has a lip to make sure the ring was pushed to a consistent depth. The hole in the middle also allowed us to pull the ring up in case we’d inserted it too deep. In our case, the ring was nearly touching and we had only three to four thousandths clearance in each cylinder.

Serving double duty, this steel plate (arrow) squares the ring with the cutting wheel and provides a stop to keep the table from pivoting into the abrasive wheel. The knurled knob on the right is adjustable and once set, makes squaring virtually automatic. We didn’t touch it after the first ring. Once the ring is square and touching the squaring plate, it is held in place by tightening the wingnut on the taller post.

With the motor off and the plate rotated out of the way to allow the table to pivot, we turned the knob on the left of the table to drive the ring toward the abrasive wheel while holding the table down. As soon as we felt contact between the ring and the wheel we stopped turning and set the dial indicator to zero.

Since we were just getting familiar with the ring filer, we moved the table .005-inch towards the wheel, turned the motor on, and made a cutting pass. Then we checked with the feeler gauge to see how the dial indicator corresponded with the indicator. It seemed to have removed a bit more than .005-inch, which we chalk up to our zeroing being slightly more than zero and perhaps .001-inch of play in the table’s pivot as we applied pressure perpendicular to the motor’s axle rather than straight toward the wheel. Our fault. From then on we were sure to only press the pivoting table straight towards the abrasive wheel. Keep in mind that .001-inch is less than the thickness of a human hair.

Taking .005-inch at a time, we crept up on the .0019-inch gap of the top ring. Don’t force the feeler gauge in place, we found that out .0017-inch feeler gauge would fit just right, but a .0019-inch feeler gauge could be crammed in the same gap.

Before the rings are considered done they must be deburred. A very light touch is all it took to knock off any accumulated metal with the fine-grit wheel opposite the gap-filing table. This can also be accomplished with a razor blade as the burr tends to be holding on by the narrowest of threads.

We’re certain that with more time with the tool a user would become even more familiar with its use. For us, we still took at least two cuts with the filer to make sure we didn’t take too much initially. We’re a little paranoid, it’s true, but we think it’s better that way especially considering that there are no extra rings in a set and you can’t add more material once it’s gone. It’s still far faster than going at it by hand. By the time we got to the second set of rings we were in a groove, cutting within one or two thousandths after our initial measurement. We’d typically cut in increments of .005-inch per pass, just to be safe and consistent.

Total Seal’s ring filer comes in at around $700, so it is on the high end for engine assembly tools for a hobbyist. However, if you’ve got multiple engine builds in your future, the time saving alone becomes worth it.

Why is piston ring gap so important?

A tight piston ring gap makes for a more efficient engine. The tighter the seal against the cylinder wall, the stronger the signal to the intake, which means the cylinder fills more completely on the intake stroke. On compression, power, and exhaust strokes, a tight gap keeps both the unburned fuel and combustion pressure above the cylinder to put more of each stroke to better use. That also keeps unburned fuel and combustion gasses out of the crankcase and out of the oil, leading to better engine longevity due to cleaner lubrication. However, too tight a gap can lead to catastrophe. The piston’s ring lands are precision machined to tight tolerances. If a ring expands due to heat and the gap diminishes to the point that the ends butt up against each other and there’s no place else to go, pressure is exerted inside the lands, which can break them.

Source:

Total Seal
TotalSeal.com
800.847.2753

The post How To Quickly And Accurately Set Ring Gap appeared first on Hot Rod Network.

The Rescue So Far

When Rollings Automotive checked out Sean Price’s 1965 Nova 350 small-block, it may have sounded badass, but the motor actually flat-lined at 4,500 rpm. For sure, there were a number of tuning and driveability bugs, but the big problems holding the car back were a “trick” hydraulic-roller custom cam with its intake lobe ground 9 degrees advanced, low valve­spring pressures, and weak early 1990s GM cast-iron truck TBI-style heads. In last month’s issue, Rollings replaced the cam with a Comp Cams Xtreme Energy XR294H-10 grind and Cloyes True-Roller timing set. This month, we address the cylinder head and valvetrain issues.

The Head Problem

At the time Price first contacted HOT ROD for help, he thought he had fairly robust 1995–1998 GM Vortec cylinder heads—not the crummy TBI heads (casting No. 810). Besides these heads’ severely restricted intake ports, the valvesprings’ installed heights were wrong. TBI-style truck heads often have extra-deep spring pockets to accommodate intake and exhaust valve rotators that can trip you up when installing hot rod springs not intended for use with rotators. The new, healthy Comp Cams grind would require even stouter spring pressures, but sooner or later they’d pull the pressed-in studs right out of the GM castings.

The obvious fix for both issues was a quality aftermarket aluminum cylinder-head swap. We wanted to save some theoretical bucks, so ideally any replacement head should not only flow much better than the crappy TBI stockers but also be compatible with the late-model 350’s center-bolt valve covers and guided rockers. Price had already replaced the inexpensive factory pallet-type rockers with full-roller guided rockers, so the cost of another rocker swap was a factor. As aluminum heads dissipate heat quicker than cast-iron, a final concern was getting more static compression out of the engine without rebuilding the entire bottom end.

The Fix: Brodix Heads

After examining various options, we settled on Brodix Race-Rite aluminum heads with 200cc intake-port runners. For this rescue, Brodix initially supplied Race-Rite castings dual-drilled for a traditional perimeter bolt as well as Price’s existing center-bolt valve-cover mounting patterns, ⅜ x 7/16-inch screw-in studs with no guideplates for compatibility with Price’s guided rockers, and (per Rollings’ specific request) stiffer springs than usual for a hydraulic-roller cam.

“Normal” springs for a hot rod hydraulic roller cam might be 125 pounds closed/325 pounds open, but Rollings believes heavy factory-style hydraulic-roller lifters need more help to avoid premature top-end valve float, so the heads came with 1.550-inch-od springs developing 155-pound seat pressures and 365 pounds open—essentially, those for a flat-tappet racing cam. The downsides: If the car lies dormant for a while, the stiffer springs may cause the lifters to leak-down, resulting in initial start-up valvetrain clatter; the installed height is slightly taller (1.95 instead of 1.90 inches); and the wide 1.55-inch spring od might cause interference issues on some installations.

Springs aside, the main reason for upgrading the heads was to garner superior top-end breathing potential. So how well do the Brodix heads flow compared to the lame TBI castings, anyway? To find out, nearby Westech Performance flowed both the GM No. 810 castings and the new Brodix heads on its SuperFlow bench (see graph).

Usually, big performance heads give up a little downstairs for midrange and top-end improvements, but in this case, Brodix proved superior at every lift point on both the intake and exhaust sides, from off the seat through 0.800-inch lift. Most relevant is the Brodix’s advantage at the peak valve-lift area (0.540 intake/0.562 exhaust) generated by Comp’s XR294H-10 cam: At 0.500- and 0.600-inch lift, Brodix was 75- and 83-cfm better than GM, respectively, on the intake side and 32- and 33-cfm better on the exhaust. In fact, the Brodix’s exhaust side outflowed the GM’s intake side at every tested lift point!

The Fix: Head Gasket

Cranking at more than 195 psi during Rollings’ initial evaluation, Price’s motor seemed on the verge of detonation with its heat-retaining iron heads. But once Rollings pulled the heads, cc’d and measured everything, static compression came in under 9:1. The original radically advanced cam had fooled us by generating abnormally high cranking compression!

A thinner head gasket is one way to gain a little more compression without major machining or disassembly. But a conventional steel-shim design won’t cut it with aluminum heads. There are fairly thin high-tech MLS head gaskets out there, but deck-surface finish is critical; Rollings was loathe to chance it with an in-service used block. Scouring the catalogs, we discovered an 0.028-inch compressed-thickness “genuine GM” composition gasket that in conjunction with the Brodix’s heads smaller 65cc (as measured) chamber raised compression to just over 9.5:1—still lower than we’d like with aluminum heads, but clearly an improvement.

The Fix: Compatibility

Sounds good, right? But you know what they say about best-laid plans. The first problem encountered: contact between Price’s guided rockers and the valvespring retainer locks that required going to conventional (nonguided) Lunati roller rockers (so much for saving the cost of a rocker swap).

This is hot rodding. Murphy’s law is our best friend.”— Marlan Davis

Not really a surprise when you swap cams, head gaskets, heads, and rocker arms, Price’s old pushrods were the wrong length—easily fixed with a set of shorter Comp Cams High Tech pushrods. At least this engine had no piston-to-valve clearance issues, even with the large Brodix 2.055-inch intake valve and rather shallow piston “eyebrows.”

Moving on, Rollings found the wide-od springs hit the bolt bosses on Price’s center-bolt covers, so he had to install new Brodix perimeter-bolt covers on the dual-drilled Brodix heads. Along with a Brodix intake, that did make for an “all-Brodix” top end.

Intake? Who said anything about a manifold swap? Another part we thought could be reused, couldn’t: There was a big port mismatch between Price’s existing high-rise dual-plane Air-Gap intake and the Brodix heads’ larger runners that are sized for a Fel-Pro 1206 intake gasket. Fortunately, Brodix offers its own single-plane (PN 1014) and dual-plane (PN 1016) intakes. PN 1014 as-cast matches the Fel-Pro 1206; PN 1016, the smaller Fel-Pro 1204—but there’s ample material to permit porting it out. We felt a port-matched Brodix dual-plane was a better fit for the street-driven Nova.

Lessons Learned (So Far)

Sometimes trying to save bucks ends up costing more bucks. If we were aware of these issues going in, the smart move would have been to order a complete Brodix top-end package that includes the heads, intake, valve covers, and every other hardware part and gasket needed to install it under one discounted part number. That saves bucks, time, and aggravation. Next month we get the carburetor sorted out by The Carb Shop, fix in-car compatibility issues and other gremlins, install upgraded MSD ignition parts, and (finally) find out if all this effort was worth it on the chassis dyno. Can we turn a mongrel into a purebred? Stay tuned.

NEED JUNK FIXED? If your car has a gremlin that just won’t quit, you could be chosen for Hot Rod to the Rescue. Email us at pitstop@HotRod.com and put “Rescue” in the subject line. Include a description of your problem, your location, a photo of the car, and a daytime phone number.

Contacts

Automotive Racing Products (ARP); Ventura, CA; 800.826.3045 or 805.339.2200; ARP-Bolts.com
Brodix Inc.; Mena, AR; 479.394.1075; Brodix.com
Chevrolet Performance Parts; Grand Blanc, MI; 800.577.6888 (nearest dealer); ChevroletPerformance.com
Comp Cams; Memphis, TN; 800.999.0853 or 901.795.2400; CompCams.com
Dart Machinery Ltd.; Troy, MI; 248.362.1188; DartHeads.com
Fel-Pro (Federal-Mogul Corp.); Southfield, MI; 800.325.8886; FMe-cat.com
John Elway Chevrolet on Broadway; Englewood, CO; 800.345.5744 or 303.761.1286; JohnElwayChevrolet.com
Lunati LLC; Olive Branch, MS; 662.892.1500; LunatiPower.com
Manley Performance Products Inc.; Lakewood, NJ; 800.526.1362 or 732.905.3366; ManleyPerformance.com
Rollings Automotive Inc.; Mira Loma, CA; 951.361.3001; Plus.Google.com/+RollingsAutomotiveIncMiraLoma
Summit Racing Equipment; Akron, OH; 800.230.3030 (orders) or 330.630.0240 (tech); SummitRacing.com
Westech Performance Group; Mira Loma; CA; 951.685.4767; WestechPerformance.com

The post HOT ROD to the Rescue: Brodix Heads Replace Restrictive GM TBI Heads on a Power-Robbed Nova appeared first on Hot Rod Network.

For the last couple years, we’ve been driving Truck Norris around with a 383 small-block Chevy under the hood and its original four-speed transmission. While that was fun, it’s time to get serious if Truck Norris is going to pay tribute to the karate-chopping badass it’s named after. Coincidentally, we’ve been working with AEM Performance Electronics on an EFI system on our BluePrint Engines 540 big-block. Impressed with the dyno-chassis results, we decided to drop that big-block into the C10’s engine bay. A move we’re certain Chuck would approve of.

Making 716 hp and 680 lb-ft of torque, our big-block demands a transmission upgrade. While the C10’s stock SM420 four-speed is probably a worthy candidate to live behind a big-block, it’s first and foremost a truck transmission. This trans is tough as nails and probably could crush rocks, but its gearing just isn’t suited to the type of driving we will be doing with our 1967 C10. The SM420’s 7.00:1 First gear was designed specifically to provide low-powered inline-sixes and small V8s extra mechanical leverage needed to get the truck moving when hauling a bed full of stuff. Other than that, it’s not used in everyday driving. Even the 3.60:1 Second gear is virtually useless with a potent small-block making anything approaching 400 lb-ft of torque. Second gear, plus the truck’s 3.73:1 axle ratio, works out to a 13.42:1 final drive. Combine that with a 27-inch-tall rear tire, and from a standing start, you have to shift gears halfway through the intersection because the engine speed is racing past 4,000 rpm, yet you’re only traveling about 20 mph. In short, the SM420 is a great transmission for a truck with a little engine, but it’s not suited for any sort of performance application, nor was it ever intended to be.

TREMEC’s T56 Magnum is a performance transmission, however. It’s the aftermarket version of the TR-6060, the very capable gearbox found under such notables as the Hellcat Challenger, Z28 Camaro, and ZR1 Corvette, to name a few. The Magnum is rated to 700 lb-ft of torque, and our sources inside TREMEC say this is a conservative figure. We’re confident it will live behind our big-block, although higher-rated versions of this transmission available from American Powertrain should you be making more power than we are. The Magnum differs from previous versions of the T56 most notably because of its wider gears, which offer increased surface area of tooth contact between the gears in the main- and countershafts. This means the Magnum will withstand higher torque levels than the previous versions found in C4 Corvettes, early Vipers, and fourth-gen F-cars.

American Powertrain provided the T56 Magnum, along with its installation kit, which includes an aluminum-transmission crossmember, hydraulic throw-out bearing, a flywheel and clutch kit, speedometer cable, and a cool shifter and cue-ball shift knob. The T56 Magnum is a very versatile transmission for aftermarket applications because the shifter can be placed in any of three different locations on the top of the transmission case. For the 1963–1972 C10s, American Powertrain mounts the shifter in the forward-most position so the shifter handle’s throws will clear the factory bench seat in all gears. Our C10 was also blessed with the benefit of having the “high-hump” floor. The transmission hump actually bolts to the floorpan; it’s an access panel to the transmission. The hump is taller than the transmission tunnel would be in a rear-drive C10 with automatic transmission, and the tall bits of the T56 fit this space perfectly. It’s as if these things were designed to have T56s installed someday!

Things are going to start moving quickly for Truck Norris—let’s see what has happened so far.

The post Project Truck Norris Gets a Big-Block and T56 appeared first on Hot Rod Network.

Raise your hand if you were a car enthusiast back in the mid-1980s when fuel injection became mandatory on OEM vehicles. Of those who raised their hands, how many of you swore that fuel injection was the death of performance? I am willing to bet that not many of those hands dropped. Back then it was assumed that once EFI (and the complicated emission systems) took over, then performance, as we knew it, would cease to exist. Thirty years later, we can safely say that high-performance and modern musclecars not only survived, they actually got stronger and better thanks to electronic fuel injection. Today’s insanity from six-second street cars to the turbocharged craze would be non-existent if it weren’t for modern technology.

Four years ago the same “bad feeling” was making its way through the performance industry and this time it was Gasoline Direct Injection (GDI) that was putting a damper on the future of performance. Manufacturers began phasing in GDI a few years ago and it has finally made its way into the high-performance line of cars like the C7 Corvette and Sixth Generation Camaro.

To put it simply, GDI is a high-pressure fuel delivery system that injects the gasoline directly into combustion chamber in each cylinder. That is a stark contrast to the low-pressure system that has been the norm in most electronic fuel injection systems as an injector (or injectors) is placed in each runner of the intake manifold. The complication of the high-pressure system, with the injectors going as high as 2,900 psi, has been the cause for alarm in the aftermarket. For the OE’s, the goal is to create better fuel economy and reduced emissions.

Enter Chevrolet Performance with its engineering prowess. The manufacturer’s high-performance division has produced a naturally aspirated version of the latest direct-injected production engine for NHRA drag racing. If you ask NHRA, they will say the 2016 COPO Camaro, with an LT-based engine, is rated at 410hp. Unofficially we are here to tell you that the engine actually produces well in excess of 600hp. What was that about GDI-equipped engines being the end of performance?

The 2016 COPO Camaro has already gone a best of 9.698 @ 137.20 mph during the Chevrolet Performance U.S. Nationals in the Stock Eliminator FS/E category. And that is without the aid of boost or nitrous oxide.

The COPO Camaro’s LT-based engine has been a blend of LT1 and LT4 production components to ensure durability as well as excellent performance. Chevrolet Performance doesn’t mess around when it comes to its validation process. The test engine was subjected to over 200 simulated drag racing pulls on the engine dyno as well as over 40 passes down the drag strip in a new COPO Camaro. The new engine’s performance was flawless, proving that GDI and high-performance can co-exist.

Don’t be too quick to write-off performance as the dawn of GDI is upon us, the factory hot rod shop is leading the way with its naturally aspirated COPO LT engine package and a—rumored—supercharged version in the not-so-distant future.

Short-Block
Chevrolet Performance takes a LT engine block and punches the bores out to 4.070-inch. The factory engine block is aluminum and features six-bolt nodular iron main caps. LT4 forged steel crankshafts are pulled off the assembly line for use in these high-winding NHRA-spec engines. The crankshaft offers a 3.622-inch throw, putting final displacement at 376ci. Chevrolet Performance turned to Callies for its Compstar connecting rods. The H-beam rods are 4340-forged steel and are 6.125-inches long. Clevite engine bearings are found throughout the rotating assembly. Mahle pistons have domed tops to help bump nominal compression to 12.4:1. Keeping it all lubricated at 8,000 rpm is an internal wet sump with a deep cast aluminum pan.

Cylinder Heads/Camshaft
Aluminum LT cylinder heads sit on top of the short-block, which feature a 316cc intake runner volume and an 118cc exhaust port volume. The combustion chamber is 53cc, which, when combined with the head gasket thickness and the Mahle pistons, gives the engine a 12.4:1 compression ratio. Chevrolet Performance went with Del West 8mm stem titanium intake valves that have a 2.205-inch diameter. The exhaust valves are sodium-filled 8mm valves with a 1.595-inch diameter. The camshaft is a steel billet hydraulic roller stick from Chevrolet Performance. The maximum lift is 0.641-inch on both the intake and exhaust lobes. The duration is 242/285 degrees at 0.050-inch lift. A set of PSI Max Life beehive valvesprings with Chevrolet Performance spring seats and retainers help keep the valves under control. Rounding out the valvetrain is a set of Johnson hydraulic roller lifters, Trend pushrods, and LT1 1.8:1 roller rocker arms.

Induction
Holley EFI was tapped, once again, for its Hi-Ram intake manifold, which was very successful on the LS-based COPO engine program. Of course the cast aluminum manifold was built specifically for the LT-based engines. It has a Whipple 90mm throttle body bolted on to the lid along with a carbon fiber air box as part of the induction system.

Fuel System/EFI
Like every COPO model before it, the 2016 version relies on an Aeromotive Eliminator fuel system from the tank to the fuel rails—or in this case up to the LT4 DI injectors. The COPO engine sees as high as 2,900 psi of fuel pressure, well within the range of the LT4 injectors. Holley EFI was also tapped for the fuel injection system as it was redesigned for use in the GDI application. NHRA has approved the HP electronic fuel injection processor for use in competition. Chevrolet Performance turned to LS7 ignition coils and secondary wires for its spark delivery.

Exhaust
American Racing Headers continues to be the supplier of the high-performance COPO headers, which are custom-made for this application. The primary tubes are 2-inches in diameter, each tube is equal length at 30-inches long, and it is all made from 304 stainless steel. A merge collector on each bank ties the primary tubes together.

Drivetrain
Backing the LT engine is an ATI Performance Products TH400 that has all the options like SFI case and 8-inch Treemaster MRT torque converter. The transmission spins a massive driveshaft, which is connected to a Strange Engineering 9-inch housing. The rear-end is filled with a Strange Engineering spool, 4.57:1 rear gears, and 40-spline gun-drilled

The post Inside the New COPO Camaro’s LT1-Based Race Engine appeared first on Hot Rod Network.

It’s Day Two of Classic Trucks Week to Wicked presented by Classic Performance Products and as we break for lunch we have a functioning suspension which includes brakes, shocks, sway bars and Panhard bar along with a fresh rearend. Now comes the time to plumb our C20/C10 conversion.

Yes, we are readying ourselves for the monster 7L LS7 from MAST attached to the Performance Automatic 4L80E tranny but there are a few less glamorous details but no less important to take care of first.

The fuel delivery system from the CPP gas tank will be handled by the HydraMat equipped Holley submersible fuel pump, regulator, filter, -6AN lines all attached via Earls fittings.
Next up is the CPP HydraStop hydraulic assist for the master cylinder. From here a CPP brake kit will link the CPP Big Brake kit to the master cylinder.

Now that we have addressed fuel supply and brake systems to handle our MAST 7L LS7 that is pumping out a whopping 702hp.

The post Week to Wicked: Day Two…It’s What’s Under The Hood That Really Counts appeared first on Hot Rod Network.

End of Day Two of our Week to Wicked presented by Classic Performance Products and we are on the verge of having a running hard and super driving C10 made from an ugly duckling C20. (Apologies to all of those C20 fans…I got carried away!).

We’ve taken a longbed long wheelbase “pickemup” and turned it into the rage of the day with a Brothers bed shortening kit, CPP front and rear suspension and braking, and an updated fuel system from Holley. Now the fun starts.

We are looking at dropping in the MAST Motorsports 427ci Chevy engine that we have dyno’ed and walked away with 702 hp and 600-plus lb-ft of torque. It’s based on a LS7 (7L) motor will be breathing through a FAST LSXrt truck intake manifold equipped with a 102mm Big Mouth billet throttle body controlled by a FAST XFI Sportsman ECU and fed via Holley fuel pump mounted in the relocated CPP gas tank and routed using Earl’s plumbing hardware. Controlling the spark will be handled by a FAST EZ LS coil-near-plug controller mated to a set of L92 truck coils. With all the modern conveniences required, we’ll be relying on an Eddie Motorsports S-Drive kit to spin all the necessary accessories on the front of the engine. To ensure the big inch LS stays nice and cool, an aluminum Frostbite radiator equipped with electric fans will regulate the under hood temps.

Transferring the power to the pavement will be accomplished via Performance Automatic Street Smart Series 4L80E. A bulletproof combination, the LS drivetrain should provide plenty of power and be as reliable as a brand new truck.

The last step today was to check exhaust fitment and also measure for a driveshaft. Remember that this truck originally had a two-piece driveshaft but now it will be a considerably shorter one-piece conventional driveshaft. The exhaust will be based on a Holley system beginning with Hooker coated exhaust manifolds and then run through Hooker Turbo mufflers.

The post Week to Wicked: Day Two…It’s What’s Under The Hood That Really Counts appeared first on Hot Rod Network.

It’s day three of the Week to Wicked presented by CPP C10 build, and halfway through the crew has made some definite headway on the project, nearly getting the short-wide to roller status.

Tuesday saw the Mast Motorsports LS7 and Performance Automatic 4L80 get installed into the truck, along with buttoning up the brake system thanks to CPP’s on-hand team. That left the building of the stainless Hooker C10 exhaust kit for Ryan to jump on first thing this morning, while Jason prepared the truck for its computer controller units (engine/trans/fuel management) and the wiring harness that’s being installed by Painless Performance at this very moment. In-between all that commotion, Christian somehow managed to squeeze the new Holley radiator into the core support and fashion up a set of hoses.

Be sure to follow Classic Trucks Facebook page for updates—including Facebook Live video—as they happen, and watch project as it nears its Friday completion date!

The post Week to Wicked Presented by CPP: Day 3 Update appeared first on Hot Rod Network.

Ken Maisano and his crew at MASCAR Paint and Auto Body in Costa Mesa, California have been hard at work finishing this 1971 Duster in time to make the Muscle Car And Corvette Nationals (MCACN) show November 19 – 20, 2016 in Rosemont, Illinois. Beginning with a relatively solid car, Kenny completely disassembled it and media blasted the shell to bare metal, revealing some rust damage in the floor pans and trunk floor. Once welded up, the crew got busy installing Reilly Motorsports’ AlterKation coil-over front suspension and the 6.4 L Gen 3 Hemi and TREMEC T-56 Magnum transmission. The rear suspension is a four-link design custom-built in-house at MASCAR.

The car will be a tasteful blend of modern and classic features, including electric brake assist, heated and ventilated seats, big brakes, a custom center console, and an eye-popping shade of modern B5 Blue. Watch for more updates and a complete feature in Car Craft.

The post Cool Hemi-Swapped Duster Nearly Complete appeared first on Hot Rod Network.

We get a thousand press releases per day, and once in a while something gets under the delete button. This time, it was a photo of a Fox Mustang with a LS swap featuring Holley’s flippable, reversible, upside-down, right-side up, Flowtech turbo headers.

So what, you say? Most DIY builders use inexpensive standard headers made of mild-steel tubing and flip them upside down. Mild steel, even when coated, will distort, become brittle, and eventually crack when exposed to the heat from the exhaust turbine. These headers are made from either polished 16-gauge 304SS stainless or 409SS stainless in black or ceramic coated. And at $189.95 for a pair, this is low-buck stuff you can abuse. They even have a 3-inch V-band flanges welded on, and the price includes clamps.

We also liked the performance specs like 1-3/4 or 1-7/8 tubing diameters, a 3-inch collector, and 7/16-inch header flange so it won’t warp and leak. We’d buy a set just for the garage art.

The Mustang belongs to Holley EFI systems manager Adam Layman. It’s a 1992 LX with a 6.0L LQ4 swap, a six-speed transmission, and an 8.8-inch rear with Strange gears, spool, and axles. He has both a 76 and 88mm turbo depending on what he is doing. His goal is to take it on Drag Week.

The post New Turbo LS Project-Car Goodies appeared first on Hot Rod Network.

Under the necessary conditions of ignition and proper burn rates (cylinder pressure history), both these conditions can exist in virtually any engine.  But, in particular, they certainly apply to race engines that are configured and tuned to operate at peak cylinder pressure during a wide range of engine conditions.  Of course, it’s known that either or both can cause damage to the affected parts, largely depending upon how serious either or both become.  Over time, we’ve encountered racers and engine builders who understand the differences between the two conditions, although there have been times when others did not.  So, as we begin our discussion, suppose we take a look at how they differ and the conditions that can lead to both.

Following ignition spark (in a normal fashion), we’d like for the ensuing flame front that travels through the combustion space to be uniform and uninterrupted.  During this process, there will be accompanying increases in both pressure and heat acting on the remaining un-burned air/fuel charges.  In-cylinder pressure analysis has demonstrated that during this portion of the combustion process, pressure in both the burning and un-burned mixtures is essentially the same.

Further analysis of this process on what is happening to and within the remaining un-burned air/fuel mixture (during this part of the combustion process) has also shown that the pressure and temperature increases as the flame front continues to advance, in addition to cylinder pressure increases by the ascending piston (just prior to TDC on the compression stroke and ignition spark).  If the un-burned charge reached a sufficiently high temperature and pressure (ahead of the advancing flame front), it’s possible that it will “self-ignite,” creating a second flame front.

Keep in mind that this self-ignition of the remaining air/fuel charge is so rapid that we can say it occurs virtually at a constant volume.  Combustion studies have shown that the speed at which this second flame front moves is much faster than what preceded it during the normal combustion process initiated by the timed ignition spark.  This greater rate of flame travel causes a pressure wave that collides with the initial flame front and combustion space surfaces, creating an audible sound (“knock”) associated with detonation.  If we boil all this down into a shorter description of detonation, we might say that it’s the result from “self-ignition” of the un-burned air/fuel charges (instantaneous combustion) that result in higher and faster flame activity following normal combustion.

But there’s another point we need to address.  Through further experimentation, that although it’s possible to heat and compress air/fuel charges to the point of self-ignition, there is a brief time period that passes prior to the self-ignition process.  This period of time is called the “delay period” prior to the act of spontaneous combustion (ignition).  Additional experimentation has shown that even though the conditions (air/fuel charge heating and compressing) can cause self-ignition, such conditions are not necessarily created during all combustion activity.  To further verify this process (by experimentation), it has been shown that by increasing the delay period, there are times when the normal flame front (created by timed ignition spark) will move through the remaining zone of un-burned air/fuel charges without causing self-ignition (detonation).

Of course, as you might expect, there are several areas to consider that can have an influence on the rate of combustion speed.  Such areas as piston speed, piston displacement, mechanical compression ratio, engine speed (rpm), air/fuel mixture ratio and combustion residue left inside the combustion space are perhaps the more prominent ones.  From a practical standpoint, probably the two of most significance to discuss would be engine speed and combustion residue left in the combustion space.

Regardless of how fuel may be delivered to an engine, an increase in engine speed will be attended by an increase in inlet air flow rate.  In some instances, we make provisions in the inlet air path to increase turbulency.  In a wet-flow environment, this can be helpful to air/fuel charge homogeneity or it can be harmful (a mechanical separation of air and fuel).  A variety of conditions can be created to improve charge quality through controlled turbulence, and we’ve even discussed some of them in previous Enginology columns.  Flow surface texture, dimpling, and the creation of swirl and/or tumble are just a few.  So, however we might choose to improve air/fuel charge quality, creating a faster burn tends to improve combustion efficiency and help reduce the unwanted tendency of end-mixture temperature and pressure to encourage self-ignition.

By comparison, we also know that combustion residue (either exhaust gas that did not exist the combustion space or bits of carbon that may become heated and glowing) can ignite end-gas air/fuel mixtures spontaneously and ahead of what was previously discussed that leads to detonation.  Particularly with respect to combustion residue, we know it is not combustible and tends to reduce combustion temperature (thus pressure).  Even a poorly-designed intake manifold can have a negative effect on reducing the amount combustion residue present in this space during subsequent firing cycles, and more often than not, relate to poor cylinder-to-cylinder air/fuel charge distribution.  Such distribution inequalities can vary among an engine’s cylinders, based not only on manifold design but as a function of engine speed.  If you conduct tests to sort out manifold design issues on an engine dynamometer, bear in mind that  distribution “fixes” determined on a dyno may vary from what you’ll see at the track.  I recall working with Smokey on his cross-ram manifold only to discover virtually none of them worked when applied to track use.  Of course, that was a so-called “box” manifold and more prone to such problems than the typical, single carburetor designs of today, but it’s still possible to see the condition occur to a lesser extent.

What can be the consequences from detonation?  Well, we’re all familiar with the mechanical damage it can cause.  Broken piston ring lands, cracked pistons, damaged cylinder head gaskets, bearing failures, and other unwanted results from both short- and long-term periods of detonation.  And, of course, there’s a loss in power derived from pistons having to work against abnormally-high cylinder pressures that produce negative work on the crankshaft and rotating assemblies.  In fact, it’s probably fair to say that just about any combustion space pressure deviations from the normal production of torque can be “felt” through an engine, in terms of lost power and potential damage.

Pre-ignition?  Thought we’d forgotten about this, right?  Let’s define this as the combustion of air/fuel charges not begun with a controlled ignition spark.  In addition, if pre-ignition begins fairly early in the normal combustion cycle, the amount of work (negative torque) being performed on the pistons will correspondingly increase, netting a loss in power…excluding possible and subsequent parts damage.  You could liken this condition to what you’d see if the ignition spark timing was over-advanced.  And, once again, if the hot-spot is sufficiently remote from the spark plug, it’s possible for the end-gas combustion pressure and temperature to build much higher than if the delay period is short, leading once again to detonation.  So it can be said that while detonation and pre-ignition are not the same condition, it’s possible for pre-ignition to lead to detonation.

Finally, from time to time in this column, we’ve touched upon specific areas that can have a favorable impact on air/fuel charge quality (homogeneity).  In fact, we mentioned a couple of them earlier in this month’s offering.  But the point in re-visiting the importance of homogeneity (from the point of fuel entry up to an including the actual combustion process) and while having an effect on power and efficient combustion, is to help void detonation and pre-ignition (or both).  You may also discover that when you’ve made an improvement in combustion efficiency (1) less initial ignition spark is required for optimum power and (2) there will be a determinable reduction in brake specific fuel consumption (b.s.f.c.), particularly at peak torque at or near the rpm for minimum b.s.f.c. (highest combustion efficiency)

And don’t overlook the importance of taking steps to reduce combustion residue.  This includes efficient exhaust ports/valve jobs and intake ports that discourage reversion.  If you’re modifying or evaluating these on an air-flow bench, try setting the exhaust valve about 80-85% for the bulk of your evaluation/changes.  And on the intake side, simply flow the port backwards while minimizing air flow back toward the intake manifold.  What this can help you determine is the reduction of reversion pulse energy back into the intake manifold (contamination that could find its way into another cylinder during its inlet cycle) and maximizing exhaust port flow to further help reduce contaminants that remain in the combustion space for a successive intake cycle.  (That’s a little “Smokey trick” for you this month.)

The post Engineology: Inside the Combustion Space – Detonation and Pre-ignition appeared first on Hot Rod Network.

The Combo

When Sean Price originally purchased his 1965 Nova, it still had the original straight-six engine and 10.25-inch 10-bolt rearend, although somewhere along the way, the trans had been upgraded to a TH350 automatic. Sean himself installed what he thought was a 1990s “NASCAR truck-series” 350 short-block with “ported and polished” Vortec iron heads and a custom-ground cam of unknown origin that—per his request—was deliberately spec’d to have a rough, raspy-sounding idle. Behind the motor, the TH350 was axed for a T56 six-speed manual trans out of a 1994–1995 Z28—the spindly 10-bolt rear, for a 3.73:1-geared, 8.8-inch Ford rearend with a Traction-Lok diff. On paper, the car should have been a kick-ass combination.

The Problem

Instead, the Thousand Oaks, California–based Nova experienced significant driveability problems. Price’s main complaint: “The car falls flat over 4,000 rpm. It stops pulling and the rpm climbs slowly. It also misses and occasionally backfires under any type of throttle input when in a loaded condition. It should be making 400 hp, but feels really low on power.” Price also mentioned he’d had a detonation problem in the past. “The new rearend’s 3.73:1 gears plus installing the stiffest possible centrifugal-advance springs in the MSD distributor—in place of the softest set I originally had in there—seems to have alleviated my pinging problem. But with my big-tube Doug’s headers, 3-inch exhaust, and single-chamber Flowmaster mufflers, it may be it’s still there, but I just can’t hear it.”

The Initial Diagnosis

Price trailered the car over to one of our favorite rescue facilities, Rollings Automotive in Mira Loma, California. A full-service facility, on a typical workday you’ll see everything from late-model grocery-getters to full-on competitive drag cars getting the Rollings treatment. As received, the car did run sluggishly with some hesitation. It did indeed idle rough (but that’s what owner Price wanted).

Initial visual inspection immediately revealed a bunch of issues;

• A four-hole carburetor spacer was installed upside-down, which could affect air/fuel distribution in the intake plenum. In general, four-hole spacers work best in restricted carb classes the engine was supposedly intended to be used in.
• The Holley 850-cfm double-pumper carb was really too big for the combination. (Price had a tired, spare 750 in the trunk, but he says it never seemed to run right.)
• Several spark-plug wires were burnt and some of the boots were damaged.
• Idle vacuum was only 9 in-Hg. This can indicate mistuning, a mismatched combo, a huge cam, and/or low cylinder pressures. Rollings says, “If the car didn’t have a manual trans, it never would have worked at all.”
• Despite the low vacuum reading, cranking compression averaged 190–205 psi. With the raspy cam, plus Price’s reported past detonation issues, it was initially thought the static compression ratio might be too high for iron heads running on pump gas.
• Weak valvesprings due to incorrect installed height: “Just 71 lbs at 1.870 inches when it should have been 125 at 1.700,” Rollings reported. Many TBI-style heads have extra-deep spring pockets to accommodate rotators on both the intake and exhaust valves; that can trip you up when installing standard performance springs not intended for use with rotators.
• Crappy cylinder heads: Not decent 1995–1998 Vortec castings, as Price thought, but early 1990s TBI truck heads! GM’s crude attempt to aid mixture motion—aka “tumble-and-swirl”—by blocking off half the intake valve-bowl approach with a vane, they’re OK for a tow-truck, but are pretty much useless at more than 4,500 rpm.

At least the spark plugs showed no evidence of detonation, although they did indicate the carb was rich.

The Dyno Baseline

Before going off half-cocked and undertaking major disassembly, we decided to baseline the Nova on Westech Performance’s fully instrumented SuperFlow chassis dyno. This would provide additional information in a controlled environment and serve as a performance baseline before undertaking more serious modifications. Rollings temporarily replaced the damaged plug wires with some extras lying around the shop, adjusted the carb idle mixture, and drove the car over to the nearby facility.

Running with Price’s four-hole carb spacer (now installed right-side up), Westech played with Price’s 850 carb as well as a known-good Rollings shop carb. Westech was eventually able to tune out an observed midrange surge while improving the overall fuel curve. The 350 was relatively insensitive to timing changes; as-received, the Nova had 34 degrees total advance, but varying the timing 4 degrees either way made no appreciable difference. Eventually, using the good shop carb, the 350 wheezed to 260 corrected rear-wheel horsepower at 4,900 rpm, a gain of about 15 hp and a few hundred rpm over the “drive-in” peak output with Price’s carb. The motor revved as high as 5,600 rpm, but was nearly flat upstairs, varying not 10 hp from 4,000–5,400 rpm before falling off the cliff. Torque finally peaked at 356.5 lb-ft at just 2,742 rpm, about a 30 lb-ft improvement. (Can we say “tow truck” one more time?) Despite the low valvespring pressure, there was no evidence of valve float; the motor’s other issues kept it from revving high enough that the springs would become a limiting factor. Able to maintain at least 6.5 psi, the mechanical fuel pump wasn’t a restriction, either.

When an engine is lazy, it’s doesn’t want to respond to normal tuning.” — Norm Rollings

The Cam Analysis

OK, so the weak TBI heads were a primary limiting factor, but what about that raspy cam? To find out just what we had, we sent it over to a nearby custom cam grinder, Steve Long Racing Cams, for analysis on its cam-checking machine. It turns out the grind was a sheep in wolf’s clothing: Considering the motor’s rough idle, the cam’s 0.488-inch valve lift and 228 degrees 0.050 duration on both intake and exhaust sides were surprisingly mild. What faked everyone out was an intake lobe ground 9 degrees advanced (see “Cam Specs” table). Rollings says the cam had also been installed in the motor a further 4 degrees advanced (for a total of 13 degrees). Good for a tow truck, not so good for a hot rod.

But why? Comp Cams’ Billy Godbold explains: “Early intake closing from a highly advanced cam will increase cranking compression, low-end response, and low-rpm torque. It will result in a louder exhaust sound due to the early exhaust opening.” In fact, static compression turned out to be low, not high: After cc’ing everything, it came in at only 8.9:1 with the GM TBI heads.

Godbold wasn’t surprised by the dyno results. “Torque will peak very early and running over 8 degrees advance will start hurting performance as early as 3,000 rpm. Yes, added cam advance is very good below 3,500 rpm, but can cost you 20–60-plus hp later. The [GM TBI heads’] small runner cross-section made that early intake closing act even earlier. Hence the very low peak power rpm, the detonation around peak torque, and it acting like it fell off a cliff on top.”

The Fix: Camshaft

There was lots of head-scratching concerning the right replacement cam for Price’s turkey. Owner Price was adamant: “Whatever you do, I want to keep the radical idle sound, but still want to drive it on the street.” Initially Rollings toyed with using a profile based on an NHRA Stock Eliminator grind with ostensibly mild 0.050 duration and valve-lift numbers, but its “cheater,” nearly square lobe profile would beat up the valvetrain under long-term street use. We finally settled on a fairly large Comp Cams Xtreme Energy shelf hydraulic-roller grind with 0.050-inch duration in the 240s. It should make good top-end power when used with complementary free-flowing heads, yet run OK in the stick-shift, no-power-anything, lightweight Nova. Price could keep his raspy idle and have his power, too.

Rollings retained the existing factory lifters, dogbones, and spider—but not the late-style bolt-on thrust plate that mates with a revised cam nose and upper timing sprocket. Old-school Rollings prefers to exercise precise control over roller cam endplay, so he spec’d the cam with an early, “retrofit-style” nose compatible with separate adjustable cam buttons and early style timing chains—in this case, Cloyes’ stout multikey Race True-Roller billet timing set, plus its two-piece front cover that has a built-in, externally accessible thrust bearing that makes it easy to achieve desired endplay without repeated disassembly. Cloyes’ cover doesn’t include attaching bolts, a cover gasket, or a front seal—but ARP, Fel-Pro, and National Seals stepped up to the plate. Note the same Comp Cams XE grind specs and matching Cloyes premium timing-set components are also offered in the late-style configuration that works with the stock bolt-on thrust plate.

The Fix Next Month

So what about a set of free-flowing heads? Well, not just heads: We also needed better ignition wires to replace the existing damaged wires that ran way too close to the headers, a major carburetor refresh, and various other glitch fixes. Next month, the Nova gets a set of free-flowing Brodix Race-Rite heads and top-end enhancements.

Contacts

Altronics Inc.
Schaumburg, IL
888.464.2587 or 847.923.0002
AltronicsInc.com

Automotive Racing Products (ARP)
Ventura, CA
800.826.3045 or 805.339.2200
ARP-Bolts.com

Brodix Inc.
Mena, AR
479.394.1075
Brodix.com

Clevite Engine Parts, Mahle USA
Farmington Hills, MI
800.223.9152
Mahle-Aftermarket.com/na/en/catalogs-%26-literature/

Cloyes Gear & Products Inc.
Ft. Smith, AR
479.656.1662 ext. 228 (tech)
Cloyes.com

Comp Cams
Memphis, TN
800.999.0853 or 901.795.2400
CompCams.com

Fel-Pro—National Seals—Sealed Power (Federal-Mogul Corp.)
Southfield, MI
800.325.8886
FMe-cat.com

MSD Performance
El Paso, TX
915.857.5200 (general) or 915.855.7123 (tech)
MSDignition.com

RockAuto LLC
Madison, WI
866.ROCKAUTO or 608.661.1376
RockAuto.com

Rollings Automotive Inc.
Mira Loma, CA
951.361.3001
Plus.Google.com/+RollingsAutomotiveIncMiraLoma

Steve Long Racing Cams Inc. (SLR)
Corona, CA
951.273.0816

Summit Racing Equipment
Akron, OH
800.230.3030 (orders) or 330.630.0240 (tech)
SummitRacing.com

Westech Performance Group
Mira Loma; CA
951.685.4767
WestechPerformance.com

Need Junk Fixed?

If your car has a gremlin that just won’t quit, you could be chosen for Hot Rod to the Rescue. Email us at pitstop@HotRod.com and put “Rescue” in the subject line. Include a description of your problem, your location, and a daytime phone number.

The post The 350 V8 in Sean Price’s 1965 Nova Nose-Dives at 4,500 RPM. We’re Gonna Fix It. appeared first on Hot Rod Network.

The days of transplanting huge old Camaro boosters onto a ’40s/’50s truck firewall are—for the most part—far behind us. Typically, behind that massive air canister is the same donor car’s pedal assembly and, just as likely, its tilt column … all of which is completely unnecessary in this day and age.

Classic Performance Products has developed an all-new firewall-mount brake booster/underdash pedal assembly—an all-in-one, compact, simple-to-install unit that’s designed specifically for your 1947-1953 Chevy. Other than the mounting/pushrod holes on the firewall, there’s no modifying whatsoever to make the bracket, or its counterpart components, do exactly what it’s designed to do: fit.

The underdash bracket incorporates an ergonomically shaped swing pedal (versus the stock pedal that requires cardio workouts to manipulate) with adjustable brake light switch and its rearmost (dash) mounting points piggyback with the factory column drop. The opposite end sandwiches the firewall sheetmetal and the exterior-mounted booster and master cylinder assembly. Simple as that.

We’ll illustrate the simplicity of the product with the following install on a 1949 Chevy 3100. Bear in mind, though, this particular truck had already been stripped down to a bare cab: no gauges, steering column/box, or stock pedal assembly to remove, so much of the dirty work is already behind us. Fortunately, none of that is imperative to the task at hand, and it will allow a much better visual perspective of the installation procedure.

The post 1949 Chevrolet 3100 – A Firewall-Mount Booster Option for 1947-1953 Chevy Pickups appeared first on Hot Rod Network.

By virtue of some of the famed powerplants of the past, classic Chevrolets have maintained a mystique that has grown legendary. Looking back, perhaps no engine combination was more responsible for the legendary status of Chevrolet muscle than the Mark IV big-block. The Chevy big-block was introduced to the public via the Corvette model line, initially as a 396-cid powerplant in 1965, growing to 427 cubes in 1966. The 427 set the performance high watermark for a generation, and that storied past is relived today in the cult status of collectability these original vehicles retain.

There were many variations on the 427 big-block theme, with the designation of the engine’s RPO option codes making up the lexicon. Two versions of the 427 debut in the Corvette lineup for 1966, with the “mild” hydraulic-cammed 10.25:1 compression L-36 rated at 390, breathing through oval port head. The more serious powerplant in that year was the 11:1 compression, Holley four-barrel–equipped, 425-horse L72. This engine featured Chevrolet’s massive, high-flowing rectangular port heads, a solid lifter camshaft, and a bulletproof bottom end containing a forged crankshaft via a four-bolt main bottom end. The raw performance of these big-blocks made a dramatic impact in the automotive world, and the Chevrolet big-block legend was born.

Choices in 427 big-blocks were expanded in 1967, with three new “Tri Power” engines, adorned with an induction consisting of a trio of Holley two-barrel carbs. The milder 400hp L-68 was based on the L-36 engine, while the 435hp L71 otherwise shared specs with the L72 of the previous year. Closing out the ranks of “Tri Power” 427s was the L89, which was essentially an L71 with aluminum versions of the large port rectangular heads. The top dog 427 was the legendary, under-rated, 430hp L88. The L88 was designed as a racing powerplant, with a serious 12.5:1 compression ratio, an 850-cfm Holley carb, dramatically beefed internals, and aluminum heads. For 1968, big-block options were unchanged, but in 1969, an addition was made to the lineup, which constitutes the Holy Grail of factory big-blocks, the all-aluminum ZL1. Exotic it may be, but don’t expect to find one sitting under a tarp, as factory production was little more than one-off. For 1970, the 454 replaced the 427 as Chevrolet’s premier big-block, putting an end to the period recognized by the mighty 427’s dominance.

Our Build

Our subject is an original 1966 vintage 425hp L-72 427 Corvette unit, the property of Corvette collector Rick Stoner, who values the historical significance of these special machines. Rick is the proprietor of Westech Performance Group, a dyno facility with enormous expertise in building extremely powerful big-block Chevys. However, Rick approached this buildup with defined clarity of the objectives. The engine would be essentially stock to preserve the pedigree of this rare and classic Corvette.

Rick’s intent was to retain the original look, flavor, and feel of his classic big-block, and for him, this ruled out such ostentatious modifications as headers, aftermarket induction, or aftermarket high-flow aluminum heads. Rick relates, “If I put on headers, a giant cam, trick heads, it’s not anything like the cars were originally. If I did all that, why not just stroke and bore it … then I might as well build an 800hp monster with an aftermarket block.” Rick continues. “At some point, all of the engine’s originality is lost, and at some point you have to then think about what’s the point of an original-numbers big-block car.” It’s hard to find fault in that logic. Rick’s approach did, however, leave some flexibility in the selection of upgraded or modified components within the build, with the objectives of reliability, driveability, and yes, performance.

To meet these goals, some changes to the pure stock combination were deemed acceptable. As Rick puts it, “You’re always going to be changing parts in a rebuild, and if a modern Competition Cams’ version of the stock cam gives me a similar feel, sound, and vibe to the original, but with more power and rpm, I’ll take that upgrade. The cam isn’t making a permanent alteration to the engine, and it is pretty transparent when in there; it just works better. If a better aftermarket Comp valvetrain will add engine reliability and performance, deal me in.” Rick goes on, “I’ll blueprint the bottom end and have Steve [Brulé, Westech’s engine builder and dyno operator] assemble it like a race engine, checking clearances, making sure everything is at the best specs for a balance of power and reliability. I’ll file fit and gap the rings for a better combustion seal than stock, I’ll use modern forged pistons with coated skirts. All this stuff was never done from the factory, but we’re just optimizing the assembly, and making sensible upgrades where the original parts are going to have to be replaced in a rebuild, like in the pistons, rings, and cam. All of these changes add up to performance and reliability through higher quality in the build, instead of making big changes to the engine’s original combination.”

While the subtle changes identified so far are aimed at performance and long-term reliability, there were other aspects of the build, where some of the factory specification was backed out in favor of improved utility and driveability in today’s world. The primary factor here is compression ratio. The factory-rated compression ratio of the L72 was 11:1, which was just right when you could pull up to the pump and ask for 100-plus octane fuel. These days, 91 octane is about the best you’ll get from pump unleaded premium. Rick’s take, “I want to just get in, fill it up on the road, and go, just like in the old days. I’m not going to want to toss in a bottle of octane booster, mix up special higher octane fuel, or worry about where to find gas to make this thing go. I’d rather just back some of the compression ratio out. That will cost some power, but with the other changes I should have that more than covered.”

Piston dome and chamber volumes are the key contributors to compression ratio with a given engine combo, and here the obvious choice to dial in the ratio was to select the appropriate piston. Rick explains, “These earlier 427s used closed chamber heads that measure around 100cc stock, and I wasn’t going to consider anything but the numbers-correct heads. With the small early chamber, the trick is to use a smaller dome to cut down on the compression ratio. For this build, I used a set of SpeedPro forged pistons, No. 2300, which have a dome volume of 16.8 cc. We found when building the engine that the valve to piston clearance on the intake side was not enough, and had the piston’s valve relief notches fly cut 0.080-inch deeper to give a safe clearance. This reduced the dome volume another couple of cc, down to 14 cc. With the pistons fitting at 0.005-inch below the decks, and a 0.051-inch-thick head gasket, the final ratio in my engine worked out to 9.86:1. That’s the true compression ratio, and it is still high enough to make good power, but is a lot safer with today’s gas and iron heads.”

The cylinder heads offered some opportunity for improved power, and also required a few mods for longevity. This began with a good, machined, multi-angle valve job. According to Rick, “The valve job was a place where I wanted the best workmanship possible, since machining the seats is a basic part of the rebuild. I didn’t skimp here. There is a power difference in how well the job is done.”

Although porting the stock heads would be a possibility, Rick decided that he wanted to keep these rare factory castings stock. As Rick told us, “I didn’t want anyone carving on these rare stock heads with custom porting, even though it would have made more power. It just doesn’t make sense to me to cut on something this rare and expensive. I did have hardened exhaust valve seats installed when the heads were rebuilt, since the seats were hammered and the no-lead gas means they’ll always be in line for a beating. The hardened seats just add durability, and I didn’t want problems down the road.” The valves were replaced with a new high-performance stainless steel set (2.190/1.88 inch) from Competition Cams. Rick explains, “I just went to Comp for the works to assemble the heads, from the valves to the springs, locks, retainers, and guideplates. I know from experience that this stuff is bulletproof.”

The cam selected is Competition Cams’ CB Nostalgia LS-6+ cam. The specs for this solid flat tappet cam are fairly stout for a replacement-style solid flat tappet. Specifications measure 239/246 degrees duration at 0.050, and a base advertised duration of 276/283 degrees measured at 0.015-inch tappet rise. Gross valve lift measures a lofty 0.544/0.539 inch, while the valve lash is kept to a tight 0.012 inch. The lobe separation is ground at 112 degrees. Plenty of number there with portents of great power.

Comparing these specs to the stock L-72 cam gives some insight into the additional performance potential, though some of the subtle advancements in cam technology and design cannot be read off a spec sheet. The factory cam came through with an advertised duration of 306 degrees, and measured 242 degrees duration at 0.050. Gross lift with the stocker was 0.520 inch, however, the lash was much greater at 0.020/0.024. While both these grinds seem similarly serious by the specs, the modern Comp grind reaches higher lifts faster by virtue of a higher-intensity lobe design, and therefore provides more area under the lift curve for better breathing and power.

Outside, the engine build would retain all of the major external cues that signify this as a stock early Corvette big-block. The factory high-rise aluminum intake manifold would sit between the heads, drawing air from the factory list No. 3247 Holley 780-cfm vacuum secondary carburetor. To ensure that the vintage carb functions as new, Rick enlisted the services of Sean Murphy Inductions of Huntington Beach, California, to fully rebuild and restore the piece. On the opposite end of the heads, the factory iron exhaust manifolds were retained, again to impart an appearance of originality in this installation.

Power Test

Back in 1966, the stock L72 big-block was rated at 425 gross horsepower. We had essentially a mildly revised version of this engine, using all stock major components. The balance was tipped with about one point less compression, but with a more modern cam profile, an upgraded valve job, and top-notch machining, assembly techniques, and replacement parts. How would the various changes factor in terms of the power at the crank? Naturally, the crew at Westech had a dyno test in mind for this in-house project, and we were eager for the results. The engine was loaded onto Westech’s SuperFlow engine dyno for the numbers. To closely simulate the as-installed arrangement, the engine was installed with a belt driven water pump, and the head pipes were bolted to the manifolds. The one compromise to originality was the installation of a modern MSD distributor in place of the factory ignition. This substitution was required since the original distributor was out for restoration, and was not available in time for the scheduled test day. A set of MSD wires were installed to direct the spark to the fresh spark plugs.

Since this was a new engine combination, there was more to do than simply fire it up, pull the handle, and record the power curve. The engine was first filled with conventional 10W-40 motor oil, and the lubrication system thoroughly primed, using a priming shaft driven by a drill motor through the distributor hole. Next, the engine was statically timed with the engine off, and the fuel system was checked, baselining the mixture screws at 1 1/2 turns out from lightly seated, and the float levels checked and adjusted, with the fuel supplied by the dyno’s electric pump. With the preliminaries out of the way, the ignition was hit and Rick’s 427 fired instantly. With a flat-tappet camshaft, break-in is critical to avoid cam failure. The engine was immediately brought up to 2,300 rpm, and the oil pressure and fuel mixture were verified on the dyno’s instruments. With everything looking good, the timing was adjusted to establish 34 degrees of total ignition advance, and the engine was run for 20 minutes to complete the SuperFlow’s automated break-in cycle. Dyno operator Steve Brulé examined the running engine with a mechanic’s stethoscope to listen for any unusual internal sounds or valvetrain maladies.

Finally, we were ready for the testing. The engine was brought up for a short sweep test, running from 3,500-4,500 rpm to get a quick gauge of the wide-open throttle mixture. The dyno instruments showed that the Holley carb’s jetting was a little outside the zone, recording a lean mixture. The dyno pull also showed that this 427 was a truly torquey beast, powering over 450 lb-ft of torque right from 3,500 rpm and holding nearly flat right to the top at 4,500. With minor re-jetting, everything proved dialed in, so we opened up for a sweep test over a broader range, extending the dyno controls to pull to just over 6,000 rpm. This time we recorded a peak power output of 451 hp at 5,900 rpm. Even with the lower compression in deference to today’s pump gas, the engine was recording higher output than the factory gross rating of 425 hp. Credit the Comp cam and valvetrain, as well as the detailed prep and assembly. The mild Rat really liked to rev, holding its torque production high enough in the rpm range to register a nice lofty power peak; 427s were known to rev, and this one seemed to confirm that reputation, making horsepower right past the magic 6,000-rpm range.

With the recorded data making us feel secure that the air/fuel ratio was right in the optimal range, additional tuning would be limited to making several pulls in an ignition timing loop to determine the optimal total spark timing setting. We proceeded and found the big-block to favor 36 degrees of total timing, which is not at all unusual for a Chevy Rat. The final best power figure came in at a surprisingly solid 455 hp at 5,900 rpm, very stout for our 9.86:1 427. The unquestionably raucous power of this “stock” Rat makes it a worthy testimony to the 427’s legacy.

The post Building and testing a 427ci Big-Block appeared first on Hot Rod Network.