The good news about our short dyno pull is that it cut off at 5,500 rpm, just before the power fell dramatically from insufficient fuel pressure. It was also good that we ran 114-octane race fuel or else there was the possibility of causing a bit of damage. As for the fuel pressure, our fuel pump was only capable of 25 pounds, and when 7 psi of initial fuel pressure was added to the 18 pounds of referenced fuel demand, that was all she wrote for the pump. While we were extremely pleased with the dyno results, we also knew our factory two-bolt block's days would be numbered at these power levels, so rather than scrambling for a larger fuel pump and increasing power, we headed in the opposite direction, looking for less boost and to ultimately tune it for the street.
To slow the blower down, we didn't want to stray from the cog setup and added a larger 54-tooth blower pulley and left the high-octane in the jug, since we still weren't sure just how radical the F2 was going to be. With lower boost levels, we knew we could run it up a bit higher on the rpm range, so for the next run we upped the ante to 6,000 rpm and were rewarded with 955 lb-ft of torque and 1,091 hp at a rather high 16 pounds of boost. At 5,400 rpm, we saw slightly less boost, 12 pounds, which made 927 lb-ft and 953 hp.
As much as we wanted to keep flogging the mill, we realized that without being able to slow the blower down, it wouldn't be feasible to put our combination in 91-octane trim. With our two days on the dyno coming to an end, we reviewed the two previous dyno pulls for what could be learned. Foremost, the F2 ProCharger is a serious kick-in-the-pants piece with the potential to make some big numbers, which it's already proven. With a max impeller speed of 65,000, our initial 18 pounds of boost at 5,400 rpm was only spinning the blower at 46,775 rpm, producing just 72 percent of its total power potential. To reach the F2's true maximum power output, we would have to spin our Rat to 7,500 rpm, which is way beyond this engine's capability. Say we had a Dart block with the forged internals; you better believe this baby would put the wow factor well in the neighborhood of 1,500-plus horsepower. How sick is that?
We have to thank Westech's Ernie Mena for fabricating the discharge tube that leads into the ProCharger Tall Boy carburetor hat, including the TIG welding he did to mount the bypass valve. The bypass valve, also referred to as the surge valve, senses manifold pressure and opens up on deceleration, releasing the excess air. Without it, the high air pressure has nowhere to escape and will force itself back through the supercharger, which can ultimately crash the impeller or ruin the bearings, creating excessive lash and destroying the internals. | 
When was the last time you saw a magazine-built engine being strapped down to concrete anchors in a dyno cell? That's right, our 496ci almost went crashing through the wall with its 1,065 lb-ft of torque. | 
Engine speed and pulley diameter ultimately determine the rpm a blower will see. Running our F2 at 72 percent capacity, we still managed to see 18 pounds of boost through our high-flowing, CNC-ported induction system on 114-octane. We should note that while we utilized a cog-drive system, ProCharger does offer a serpentine system. But to eliminate any belt slip, the cog is the only way to go. |