He continues, "We knew the engine would operate on 89-octane at times, so we limited its compression ratio to just under 10:1. Wisely, 92-octane was used during the dyno session, and this is likely why it peaked with 42 degrees of total timing instead of the normal 36-38 we see when combining Edelbrock heads with 92-octane fuel. I'm confident it will produce similar peak power numbers with less timing when running on 89-octane; I suggest that timing be set to 38 degrees in those conditions."
Butler says he's pleased to see horsepower peak at 5,500 rpm-a relatively low number for a combination such as this. "It carried over 530 lb-ft of torque for nearly the entire pull, and that should make for a great street engine that can be driven in any situation with little to no maintenance. I think the team at Restore A Muscle Car will be very happy with this combination."
Hall contends, "I really didn't know what to expect going into the dyno session. There are countless factors that can affect the outcome, but we've always had great support from the team at Butler Performance, and David was there to assist every step of the way. I'm very pleased with the results, especially knowing that I can pull into any gas station, fill the tank with 89-octane fuel, and still produce that much horsepower. It's certainly a combination we'll offer to our customers."
Conclusion
While additional compression and extended camshaft duration and valve lift might yield greater output from the 474ci, few will argue that 578 hp and 588 lb-ft of torque aren't impressive, particularly when considering the parameters set forth. Once installed, it should perform admirably in virtually any condition while maintaining excellent drivability at all speeds, and that's exactly what this customer ordered.
A point to keep in mind about our feature build is that not only does it highlight the power a moderately built Pontiac produces, it also proves that hobbyists needn't be professional engine builders to achieve such results. With precise block machining, any technician or competent hobbyist can assemble a large-cube mill like this with minimal effort-and seeing it generate 578 hp makes that effort worthwhile.
Wth the rod bearings and caps...
Wth the rod bearings and caps now installed, and having already checked rod-bearing clearance and rod-side clearances during preassembly, Otto applies a coating of ARP moly-lube to the bolt threads and tightens each to a final torque spec of 75 lb-ft.
Here is the bottom end awaiting...
Here is the bottom end awaiting the oil pump, pickup, and pan installation.
From the topside, the flat-top...
From the topside, the flat-top pistons with valve reliefs are revealed.
Otto installed the adjustable...
Otto installed the adjustable timing set from Butler Performance and employs a Comp Cams camshaft degree kit to position the cam at the suggested intake centerline of 106.5 degrees.
Butler Performance prepared...
Butler Performance prepared a pair of 87cc Edelbrock aluminum cylinder heads specifically for Hall's build. The intake and exhaust ports were hand-massaged by Butler Performance...
...and the supplied specification...
...and the supplied specification sheet reveals that airflow at 0.700 inch is 316 and 236 cfm respectively at 28 inches.
Normally milled to minimize...
Normally milled to minimize volume after polishing, the combustion chambers of this pair measure 90 cc's, which produces a compression ratio of 9.95:1 with 474 ci. David Butler feels this is compatible with 89-octane fuel.
The Victor intake manifold's...
The Victor intake manifold's large plenum and smoothly contoured runners provide good flow characteristics at high rpm without grossly sacrificing low-speed throttle response. Hall will perform some modifications to the Trans Am's air cleaner to accommodate its original Shaker hood.
While the 2.11-inch intake...
While the 2.11-inch intake valve is retained on the E-heads, the exhaust valve diameter is increased to 1.77 inches. The valvesprings complement the hydraulic-roller camshaft's profile.
After Otto installs the cylinder...
After Otto installs the cylinder heads onto the short-block and torques the ARP head bolts to 85 lb-ft using moly lube, he drops the Comp Cams-supplied hydraulic-roller lifters, hardened pushrods, and 1.5:1-ratio roller rocker arms into place. Lifter preload was set to 3/8 turn beyond zero lash.
After installing a host of...
After installing a host of ancillary components, including an aluminum valley pan, a Canton oil pan, a Demon carburetor (shown here getting its jets changed) and an MSD HEI distributor, it was dyno time for the 474 at Spanel Engines in Lincoln.
Timing was adjusted a few...
Timing was adjusted a few times during the session. Note that we utilize a previously used pair of tubular headers with 1.75-inch-diameter primaries and 3-inch collectors. This was to prevent tarnishing the silver ceramic-coated Doug's Headers installed in the vehicle.
At the console of the Superflow...
At the console of the Superflow SF-901 engine dynamometer sits Chuck Spanel. After proper engine warm-up, he starts each pull around 3,200 and allows the computer software to increase rpm 300 per second until it reaches approximately 5,800. A series of eight pulls were made, each incorporating a plethora of carburetor and timing settings. Corrected peak power numbers of 578 hp at 5,500 rpm and 588 lb-ft of torque at 4,700 rpm were achieved with No. 81 and 89 jets (front/rear) in the Demon carburetor and 42 degrees of total spark lead.