Dyno Video: Pfaff Big-block Chevy Built for Super Stock Boat Racing

The 427ci big-block engines in APBA Super Stock boat racing are subjected to flat-out 5-minute runs that can be interrupted with 180-degree turns, depending on the course layout. The torque and rpm requirements are very demanding, yet the rules are extremely restrictive. The engine builder has little leeway in parts selection and modification.

This BBC built by Gordon Jennings at Pfaff Engines for national champion Dave Rankin pumps out more than 660 horsepower at about 7,100 rpm with peak torque of 560 lb-ft between 5,500 and 5,800 rpm.

“It’s a short torque band,” says Jennings, adding that the 18-foot flat-bottom boats are limited to 1,950 pounds and 112-octane fuel. “As soon as you stand on the gas, these boats will straight to 6,000 rpm, because the prop slips and then it pulls you right up to 7,500 rpm.”

The engine starts with 427 block with a maximum overbore of .060 inch, and a flat-tappet cam is mandated. Spec JE pistons are required along with a Dart 310 cylinder head and GM dual-plane intake manifold. Porting and other modifications are not allowed to the heads or manifold, and carb spacers are restricted to 1.5 inches. Any carb can be used but the throttle-plate diameter is restricted. Ignition is limited to a points-type distributor or HEI.

“With the spec piston, you can only put in so big of a cam,” says Jennings. “Getting the duration right with the lobe center and as much lift as you can get makes it all work right. Playing with the duration is about all you can do since you can get only about .700-inch lift.”

Jennings uses a 3.760-stroke Callies crankshaft, Manley steel rods and a custom-designed Dan Olson oil pan.

“The oil pan makes power,” adds Jennings, noting that the little touches and attention to detail provide some leverage in adding power. “There’s a crank wiper. We make sure every combustion chamber is exactly 117cc and deck the block right. It’s all important stuff when you’re working in a spec class.”

 

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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