Supercharged Pontiac in High Performance Pontiac
 

Article in High Performance Pontiac (by Ray Bohacz) about a Paxton Supercharged 467 cid (4.185" bore/ 4.250" stroke) with an Butler/Eagle Forged crankshaft and a set of ported cast iron heads. The 6X heads (96cc) flowed 250/186 cfm at 28" test pressure at .600" lift.

An outfit called Gear Head Designs provided the Paxton Supercharger Kit and a machine shop/ dyno place called Racekrafters Automotive Machine, I assume, did the Machine work/ engine assembly/dyno testing.

To cut to the chase, at 7psi boost at 5200 rpm they made 647 hp and they made 680 lbs/ft of torque at 4500 rpm. (That ought to move the old Pontiac down the road in a brisk manner). They tested with a Snow Injection System, with an air/air inter-cooler, and 100 octane plus "Rocket Fuel" gasoline. Not bad numbers really for a cast iron head engine with 9 to 1 compression, GOOD GAS, and a small 224/230 Hydraulic Roller camshaft with .552"/.561" lift on a 110 C/L camshaft.

As a comparison, a couple of years ago, Luhn Performance tested a 462 engine with 2-bolt mains and a Scat Forged crankshaft, with 310 cfm (mildly ported) aluminum Edelbrock heads, a slightly lower compression ratio, and a slightly larger camshaft to match the extra cylinder head flow. The superchargers were basically rated the same HP 820 HP for the Vortech unit vs 825 HP for the Paxton unit. (Both superchargers are made by the same company that owns both Paxton and Vortech). They just look different on the outside of the case.

At the same 5300 rpm, the Luhn set-up made 863 HP and 891 lbs/ft of torque at approximately the same rpm as the testing above.

The differences as reported above were: 1/2 point lower compression ratio, 20 degrees more camshaft duration, 60 cfm more head flow, a water-to-air inter-cooler (vs the air to air unit used above) and 6 more psi of boost (13 psi).

So basically this confirms that you can easily have a mild 600 hp set-up or you can have a slightly more expensive aluminum head set-up with a different tune-up and make an easy 200+ more horsepower (by turning the boost up a few more psi) at the same rpm.

Tom Vaught

Nice little project... I think a 400 could be built to same levels just adjusting the rpm range up a bit. A little cam refinement and cut back compression a bit closer to 8:1 you could get those numbers on a pump gas 400. Glad to see the iron head too... IMO they will hold a gasket better/longer.

If I would get my butt in gear I could tell you what a YSi and a solid roller with the same e-heads would put down:D.

Tom did luhn use d port or round port heads ?

I'm coming back with my little 400 that I showed on here a while back
on a test stand, Made ruffly 600 HP @ 7:98:1 comp
This time bigger cam about the same comp, Hoping for 700 HP on pump
gas. This time it will go on the dyno. Maybe a little N2O too for maybe 800.
Will see. Later on that project. Oh Ya Blower motor.

GT

Tom, what are your thoughts on using a blowthru carb hat on a 4 barrel throttle body with MFI? I’d like to run a Vortech YSI on my 484 but hood clearance is an issue due to running highports. I refuse to cut the hood in any way. I’m switching to Holley Terminator X MFI with a 4 barrel throttle body (only 2” tall which helps).

With the Victor and Dominator I can’t get an air cleaner on under the shaker hood. The front on the Dominator is maybe 1.8” from hitting the shaker. If my calculations are right I should be gaining about 3.2” of clearance with the new MFI setup.

When you are only moving air from the Vortech supercharger thru a bonnet, thru the basic 4BBL throttle body then thru the MPI manifold the air distribution tends to even out more (at least to the point where you can change the duty cycle of the injectors "somewhat" to make the runner air fuel ratios close. The bonnet has a effect but you can tune around that effect if you have individual control of the injectors.

In my opinion a better way is to put a large single bore throttle body between the supercharger and the elbow feeding the intake manifold. The Blade effect of the TB is a lot less on what air the different runners see at the port injectors.

Tom V.