1. With a valve cover removed,...
1. With a valve cover removed, we get a sneak peek at the valvetrain. A special feature of the Crower aluminum roller rockers is that when oil comes up the pushrod, it is directed through the rocker to the tip of valve and roller tip to cool and lube them rather than flowing over top of rocker and on to the cylinder head. Smith Brothers pushrods are made from chrome-moly. They are seamless, very strong and very light. Crower valve springs were matched to the cam requirements. Also visible is the Flowcooler aluminum water pump and the harmonic balancer from BHJ, which is made from steel with injection-molded rubber and is SFI approved for racing.
2. The heights of the Holley...
2. The heights of the Holley and Rochester carburetors are measured to determine the difference, which is nil as both measure 3.25 inches from the base to the air cleaner mounting surface.
3. With the carburetor removed...
3. With the carburetor removed and turned over, the flange differences and bolt hole spacing between the Holley used on this engine and the Rochester Quadrajet on the right are readily apparent. You will also notice the equal bore sizes (square-bore) of the Holley for performance vs. the small primaries and large secondaries (spread-bore) of the Rochester, which is a concession to economy and crisp off-idle throttle response. Holley has long been known for building high performance street and racing carburetors that offer power but little economy, at least in square-bore form (Holley has spread-bore carbs too) and the Q-jet has been relegated to economy status and generally gotten a bad rap as a performance carb due to its design and perceived tuning difficulties. However, both can be successfully modified to perform in either arena.
As stated in Part I, HPP was introduced to this project by a phone call from Jim Taylor who had just finished running the potent engine on the Bitner Automotive Inc. dyno to seek out its power limits. As a result, our two-part story includes the tear down, in Part I, which illustrated the wear created during the flogging and now we will discuss the components, machining and massaging required to produce 509 horsepower. View it as a reverse buildup if you will, as the photos will depict the motor coming apart rather than the usual bolting together.
This engine is tailor-made for the portly option-laden Second-Gen. T/A, which can tip the scales at nearly 4,000 pounds and has a carb height requirement due to the shaker hood scoop. The single-plane Holley Street Dominator intake manifold, which was employed on this engine, can be worked to produce the power levels seen in this story at the desired rpm while fitting under the hood. Whereas the Edelbrock Performer intake, another aluminum aftermarket piece that is known to fit under a shaker setup without a problem, will begin to drop off in power due to its dual-plane design, right in the rpm range where the Street Dominator thrives. Bear in mind that the Street Dominator for a Pontiac is no longer sold by Holley and will have to be found at swap meets or in classified ads.
Jim also related that the 850 Holley carb used in this buildup is his engine break-in carb and possibly a 750 carb would increase velocity further and may make more torque. This prospect opens the door for the Q-jet, which could be tried on this engine and would ensure that no mods whatsoever would be needed to the air cleaner base to fit the carb, as may be the case with the Holley.
The option to retain the stock valve covers is also important to Second-Gen. T/A owners because taller units often interfere with the stock brake booster and A/C brackets. This engine will allow the use of the stock valve covers.
Another enticement is that a 428 crank was fitted to the 400 block, making possible 440 cubes in an engine, which from all outward appearances is a 400. It's a sneaky way to be a street hero, when your 400 seemingly produces ungodly amounts of power for its perceived displacement.
The crank installation was accomplished by turning down the mains to 3.00 inches from 3.25. But that's not all that is required. The process has been mired in controversy for years with engine builders taking a stand on either side of the issue from a reliability standpoint. Turning down the crank is no big deal for this rpm range, but the method by which the width difference between the thrust bearings for the 400 and 428 is corrected is. Taylor explained, "The issue of the thrust bearing width difference between the 400 and 428 is commonly addressed by welding up the 428 crank's thrust face. I don't weld cranks. We use a heavily modified Olds V8 thrust bearing. Thrust is set at .008."
According to Taylor, "This engine combination works because the small ports combined with roller cam and the 4-inch stroke provide great torque and throttle response at all rpm points. With the chosen valvetrain components, stock valve covers can be retained and the height of the Street Dominator intake allows a shaker scoop to be reinstalled. Customers report that a 3.08 or 3.23 rear gear is all that is needed for peak performance. The only drawback is the 11.5:1 compression ratio, which requires 108 octane fuel."
Taylor reports that he can build a similar combination with 6X heads and 9.5:1 compression, and a slightly different cam, which will produce 25 less horsepower but retains the same torque figures and runs on pump gas. The cost for the 11.5:1 or the 9.5:1 engine is approximately $8,500 and requires no core from you. Read on to learn more.