Dyno Video: Blown Big-block With Mild Setup Makes 1,375 Horsepower

It seems that drag racers can always be talked into building an engine that’s bigger and more powerful than what they first wanted.

The owner of this menacing 555ci blown and methanol-injected big-block Chevy at first ordered a small-block with an 8-71 supercharger, then was talked into big-block with a same-size huffer. After a little more bench racing with his buddies and budget talks with his wife, the decision was to go with a BDS high-helix 10-71 supercharger and build in a little overkill with the parts selection to ensure durability and leave room for plenty of improvement.

“It’s only at 9.5 pounds of boost right now,” says engine builder John Himley of CNC Motorsports in Brookings, South Dakota. “We’re at 1,375 horsepower (final dyno after video pull) and still climbing. It’s capable of making 1,700 to 1,800 horsepower.”

This big Rat is scheduled to power a drag truck in a non-electronics class; hence, the mechanical fuel injection.

“He’ll also be foot-braking it,” sighs Himley, thinking of the 1,000 lb-ft of torque the engine makes from 3,800 rpm and up (peak is 1,094 lb-ft at 5,300 rpm).

The engine is based on a Dart Big M block bored to 4.560 and fitted with a Callies forged steel crank with a 4.250-inch throw. Rounding out the rotating assembly are Oliver rods, custom Diamond pistons (10.75:1 compression ratio) and Total Seal rings. A set of AFR 345cc as-cast heads were bolted on after the springs were changed and an Inconel exhaust valve swap.

“Since it’s a boosted engine, the ports weren’t that critical, so we went with off-the-shelf heads,” adds Himley.

A custom Comp Cams solid roller (276/290 at .050 with .775-inch lift) motivates the 1.7:1 shaft-mounted Jesel rockers.

On top is a BDS 10-71 supercharger with high-helix rotors and an Enderle mechanical fuel injection with traditional bird-catcher scoop. All are black annodized for an intimidating appearance. Rounding out the build is a Mallory magneto.

There’s plenty of room for upgrades, according to the crew at CNC Motorsports. A change of pistons, tougher rod bolts and overdrive pulleys could easily add a few hundred more horsepower if this go-fast truck driver wants to go even faster. That is, if his foot can hold the brake at the starting line!

About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World.
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