Double Blower Realities

These two Stage 2 BDS blowers are capable of flowing 435 (8-71) and 411 (6-71) ci of air per revolution each when run 1:1 with the crank. The NOS can add a 300hp shot, but to use it all at the same time requires a large bucket to pickup the scattered crank and connecting-rod shrapnel.

To be realistic, this 474 can get all the air it will ever need from the single blower; Bill knows that. With the 6-71 single blower and a mismatched previous torque converter that had a 5,500 stall, the 3,300-pound (3,500 with driver) GTO ran the quarter in 10.26 at 122 mph on motor, 8 percent underdriven, and at just 4 psi of boost, according to Bill. He recalls: "The stall speed was totally wrong for the combo, and the car was 'blowing through' the converter. As a result, the engine was bouncing off the 6,800-rpm rev-limiter chip from the 1/8-mile to the traps."

Bill is looking for 9-second timeslips with the new tighter converter, but he also admits that the second blower, while it looks killer on the street, will probably be more of detriment to that goal than a help due to the amount of horsepower it takes to drive it, amount of heat it will generate while delivering air to the blower beneath it and the engine despite the intercooler, and the fact that the single 8-71 is large enough to feed the engine anyway. He also realizes that should the second blower offer a performance benefit, the reward will probably cause a hasty evacuation of the contents of the short-block.

For those reasons, Bill is planning on yanking the 6-71 blower and heading back to the track with the single 8-71 13-percent overdriven to make some more passes with increased boost.