Back in May, EngineLabs Magazine asked readers to send in questions for SCAT Crankshafts‘ founder, Tom Lieb. Now, he’s answered 10 questions related to all things crankshafts, connecting rods and pistons.

Check out one of the questions readers asked and Tom Lieb’s answer:

What are the unique requirements of the crank and rods when turbocharging a 1,000-horsepower street engine turning no more than 6,500 rpm. I am building a twin-turbo ’70 Boss 351C, and debating how much stroke to use, 3.750, 3.850, or 4.000. I still want decent gas mileage on long highway runs but need the torque to pull the twisty mountain roads. How much strength do you need in this application; cast, forged, or billet crank? Also, some say don’t use H-Beam rods, only use I-beam rods; which rods should be used?

-David Parks


Tom Lieb: David, for your application, a forged crank is a must, but a billet is “overkill.” There are various I-beam rod designs on the market, some of which can be marginal for strength. You can’t go wrong with an H-beam rod. Turbocharging is a substitute for cubic inches and for less oxygen available in mountain driving. The challenge is to get a piston, combustion chamber size and stroke combo to obtain a low-enough compression ratio to support your street application.


Read all of the questions and Lieb’s answers on