Q: I’m in the process of resto-modding a GMC pickup.

The truck is currently equipped with a 5.7L 350, overbored to .040”.

First, how do I figure out my new displacement?

Second, I’d like to achieve about 375 horsepower and 375 foot-pounds of torque. Can you make some recommendations about the crank, camshaft, lifters, pistons, and rods? I’d like a nice lope in the cam. I’ll be running with some Mickey Thompson Baja Claw tires, and I’d like to get them smoking.

A: First, here’s the formula for finding the displacement of a 4-, 6-, or 8-cylinder engine:

Cubic Inch Displacement (C.I.D.) =
Bore x Bore x Stroke x 0.7854 x (Number of Cylinders)

Stock bore on that V8 engine is 4”, plus the .040” overbore; stock stroke should be 3.48”. Plugging in the numbers for your engine yields 356.88, or 357 c.i.d.

There are several variable to consider in your quest for more horsepower. Given the information you provided, here’s one plan you might consider:

A popular conversion for the 350 engine is to swap in a machined 400 crank, thus converting it to a 383 with a .030” overbore). Summit Racing has 383 engine conversion kits that come with much of what you’ll need, including things like the crank, rods, pistons, ring bearings, gaskets, and oil pump.

We can also recommend an COMP Xtreme Energy cam, Edelbrock Performer intake manifold, and a Holley 670 carburetor, and believe that will get you to those power and torque numbers you’re looking for.


This is another in a series of weekly Q&A Mailbag sessions with Summit Racing‘s tech department, in which there are hundreds more. Click here to see them all

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Author: Dave Matthews

Dave Matthews was a mechanic for the U.S. Army, a Ford dealership, and served for many years as a fleet mechanic for construction companies. Now a technical content producer at Summit Racing, Dave has spent decades working on everything from military vehicles to high performance race machines.