Supercharged 496 Motor - Long Rod Rat

Build The Ultimate Torque Monster-A Stroked, Supercharged 496.

Mark Daniels Jan 30, 2007 0 Comment(s)

Our first pulls on the Jim Grubbs Motorsports dyno were intended to squeeze maximum yield from the long rod 496. We locked the timing in at 30-degrees, put the small pulley on the blower, and filled the fuel tank with 110-octane race gas. After a few pulls, we found that 80 jets in the primaries and 86 jets in the secondaries worked best, and the boost gauge was peaking at 12.5 pounds. That's a lot of boost, but the numbers made our jaw drop. The torque curve was nearly flat, running over 600 lb-ft from 3,000 rpm to redline, with a peak of 836.7 lb-ft at a relatively high 4,800 rpm. Power doubled from 3,500 to 5,300 rpm, where it peaked at 855.2 hp.

Our second setup of the day was a more conservative setup. The big blower pulley was bolted on, which produced a significantly more conservative 5.5 pounds of boost. We swapped in 78 and 82 jets for optimal air/fuel, and dialed the timing back to 28 degrees. The fuel tank was drained and filled with 91-octane gas from the corner station. While not as awe-inspiring as the race-gas figures, the motor still made well in excess of 500 lb-ft of torque throughout nearly the entire rpm range, with a peak of 688 lb-ft at 4,900 rpm. Horsepower peaked at nearly 700 at a relatively low 5,500 rpm. Overall, running the engine in pump gas trim lost 157 horsepower and 148 lb-ft of torque, but with average numbers in the high 500-range, this mill could still propel a well-prepped street car into the 10s on pump gas.

Sources

Cometic Gasket, Inc.
Concord, OH 44077
440-354-0777
http://www.cometic.com
Holley Performance Products
Bowling Green, KY 42101
270-781-9741
http://www.holley.com

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