A R T I C L E S
Double Punch ! - 775hp with 2 Blowers
The Engine That Ate My Brain - By Scott Parkhurst
Supercharging, turbocharging and nitrous oxide injection are all evolving at a fast pace. The beauty of this for hot rodders like us is that all of these methods of producing increased horsepower are becoming more varied, more specialized, and more flexible. The need for a powerplant capable of producing huge power on pump gas is easy enough to understand, but being able to achieve this with daily-driver realiability on a relatively uncommon engine proves that is can be done.
Bruce Kent is the owner of this particular Buford, and his goal was to create an engine with plenty of visual appeal, and the sauce to back it up with some real power. Working closely with Jim Bell and the crew at Kenne Bell, this extreme application is much closer to the mainstream than it may appear. Soon to find a happy home in Bruceīs ī70 Buick GS, expect this pressurized V-8 to power the heavyweight A-body toward the nine-second range on the track, while being docile enough to hit cruise night on the way home.
Starting with a ī70 455 standard bore block, Bruce overbored the cylinders a minimal .007-inch to achieve a fresh surface, and allow the use of a standard Mopar 440 piston. This allowed him a wide range of pistons and rings, of which he took full advantage. He also also planned to use a longer Pontiac connecting rod, which is is also readily available, and provides a better rod/stroke ratio. The bores now measure 4.320 inches, and are filled with Ross pistons that have been machined for use with the 6.625-inch (.025-inch longer than stock Buick) Eagle connecting rods that were designed for use in a Pontiac. The Kenne Bell piston rings are designed for both street and strip use, and measure 5/16-inch thick on the top and second rings, and 3/16-inch thick on the oil control rings. The pistons have been designed to provide a statci 8:1 compression ratio, allowing the supercharged big-block to survive on pump premium on cruise night. With good stock crankshaft, the reciprocating assembly came together.
These are two primary areas of concern when building a big Buick. The bottom end needs a bit of reinforcement, and the oiling system needs to be upgraded for high rpm use. Bruce has addressed both of thses areas with assistance from Kenne Bell. A bottom-end girdle has been added, which distributes the load on the bottom end over a much larger area. With this modification in place, other 455s have been spun to a heady 7,500-rpm without failure.
In the lubrication department, the blueprinted oil pump has been treated to one of Kenne Bellīs booster plates (PN KB18213), and in sybc with the deeper pan, pickup, windage tray, and custom scavenging line Bruce has added, directing the dead dinosaur juice will not pose a threat. Bruce is also employing a remote oil filter setup from TD Performance, which will add to the capacity of the system and allow him to run a Ford oil filter with an internal bypass.
Buick cylinder heads flow pretty well, and are one of the advantages to running a Buick at all. With a valve upgrade, the heads are identical to Stage 1 units, and they have gone through Kenne Bellīs porting gauntlet for additional flow. Feeding pressurized air and fuel to the 475ci mill will not be an issue. Since this is a supercharged application, the heads have been O-ringed and fitted with copper gaskets for maximum sealing.
The camshaft is also one of Kenne Bellīs designs (PN TS228), and provides a smallish .490-inches of lift and a mere 280-degrees of duration on 112-degree lobe centers. This admittedly small grind will provide suitable idle quality and crisp throttle response, while allowing the superchargers to make the additional power under boost. Being a hydraulic, flat-tapped design, maintenance needs are minimal. The juicy tappets feed lift up through hardened pushrods and Kenne Bell 1.6:1 roller rockers.
The induction system is based around the quad-rotor Kenne Bell superchargers, fed by twin Holley 4150 HP-series 950-cfm carbs. These superchargers expel 2.1 liters of air(and fuel) on each revolution, and if you look at a 2-liter bottle and think about it for a minute, thatīs a lot of air. Both superchargers have a dedicated bypass for when Bruce finally letīs up on the throttle, and excess pressure is bled out of the plenum and back into the upper portion of the blower. Boost is built inside the superchargers instead of inside the intake manifold, and the screw-rotor design means no pulsating like other Roots designs. The homogenous mixture of air and fuel is superbly mixed, resulting in a very efficent burn. These superchargers do not create as much heat as Roots blowers, nor do they require as much power to turn.
The intake manifold is an old Offenhauser dual-quad manifold that has had the carburetor mounting pads machined off. A Weiand 6-71 blower mount plate was then welded to the Offy base. The twin supercharger assembly was designed to mount to common 6-71 intakes, thus simplifying the task of adapting the induction system to less-common powerplants. Any 6-71 intake manifold could be used as the basis for a quad-rotor buildup like this one.
An electronic fuel injection system is also available for the quad-rotor application, at additional cost. Mounted to the rear of the compressors, the system provides a lower profile in addition to reliability of EFI.
All of the braided steel lines are from XRP, and a Holley fuel pressure regulator monitors the go-juice fed from a Holley electric pump, augmented with a Kenne Bell Boost-A-Pump.
The ignition system must be solidly engineered for reliable performance, and Bruce depends upon MSD components throughout. The plug wires are Kenne Bell, and are protected at the plugs by TD Performance cloth heat shields. The MSD cap is one of their new large-diameter models that include spark plug-type ends, a wide diameter(to avoid crossfiring), and a retainer cap the ensure all plug wires are secure.
Other details that separate this Buick from masses include an ATI balancer, TD Performance return springs, Made For You wire separators, and a lightweight Mallory starter. The starter is a very trick piece, with lock collar that can be loosened, allowing the starter body and solenoid to be rotated to the best possible location. This would be a great aid in keeping clear of header pipes or any other possible obstructions. We think Mallory has a winner in this flexible part, and if it fits on a Buick, you can bet Pontiac, Olds, Cadillac and Chevy owners will find it usefull as well.
Building a supercharged engine for both street and strip use is often a compromise toward one or the other. The recent developments in high-effiency superchargers continue to bridge this gap, and the building of a Buick-based powerplant to excel on both ends of the scaleshows how far weīve come. The future of supercharged powerplants is bright on both the OEM level as well as the aftermarket, and youīll continue to see the latest and greatest means of, extracting horsepower from all sources here on the ICE-NDRA homepage.
This article was posted in PHR (Popular Hot Rodding) Sept. 1999 issue