The Chevy 377 De-Stroker
Jim Russo
Redding, CA
I'm going to build an engine for my '67 Biscayne, and I have several options available but I'm interested in doing a 400 small-block with a 350 crank. I can't seem to find much reliable info on this. I remember reading about this combination quite a while back but don't remember the specifics, such as who makes the bearings and pistons and which rods would be used.
Terry Mcgean: That engine combination was more common back in the late '70s and into the '80s when rodders seemed to believe that a big stroke like the 400's couldn't be run hard reliably. You see it much less frequently these days, as big-cube small-blocks are now en vogue and it's been proven that even a 434-inch Mouse can be thrashed repeatedly if built right. However, the big-bore/ short-stroke combo that results from the 350 crank in a 400 block still has its merits. This recipe yields 377 inches when combined with a 0.030-inch overbore (4.155 bore, 3.48 stroke), but the advantage beyond the extra cubes lies with the bigger bore, which allows better cylinder filling as the valves are less shrouded than in a typical 4.030-inch bore, as found in a rebuilt 327, 350, or typical 383.
The problem is that the 400 uses larger-diameter main bearings than other small-block Chevys. There are two options for putting the smaller 350 mains into the larger 400 block: spacer bearings used in conjunction with stock-style bearings, or special thicker bearings. We recommend the latter, and you can get them from Speed-Pro or, oddly enough, from Comp Cams.
Most 377s use either 350-style 5.7-inch rods or aftermarket 6-inch rods. The rod used determines what pistons will be employed, though most performance piston manufactures have off-the-shelf offerings for this combination. Try KB Performance Pistons or SRP for slugs.
David Freiburger: Dude, you're killing yourself with the 377. The only reason to build that combo these days is because you need to fit a cubic-inch rule for racing or because you have the parts sitting around and don't want to spend any more money for a longer-stroke crank. The extra 30 or so cubic inches you'll gain from sticking with a longer 3.75-inch 400 crank is far more beneficial than any gain you'll get from the smaller stroke's theoretically better bore/stroke ratio. Especially if we had a big Biz, we'd take the cubes.
Also, if you do want a 377, don't forget that big-bore aftermarket blocks can be ordered with 350-style mains so you can use regular bearings.
More Info
Comp Cams
Memphis, TN
800-Cam-Help
compcams.com
KB Performance Pistons
Carson City, NV
800/648-7970
kb-silvolite.com
SRP Pistons
Redondo Beach, CA
714/898-9763
jepistons.com
Special Service
Cory Grimes, Royal Oak, MI: I have an '86 Mustang LX with a 5.0L and a five-speed. The car has lots of bolt-ons and plenty of abuse from previous owners, but I'm attempting to bring it back to a more stock look with a reliable combination. I've got a new short-block with aluminum GT-40 heads, an E-303 cam, and a Cobra intake, plus some smog-legal shorties, a high-flow cat pipe, and a cat-back system. But my question is about the exterior. Since my car is a sedan, I thought it might be cool to give it the cop car look, even though it's not actually a Special Service Package (SSP) car. I have a set of aluminum "10-hole" wheels that I'm currently prepping to paint black, but I was told on a Web site that an '86 Mustang cop car would have had steel wheels. Is this correct? I don't want to put 14-inch Fairmont wheels on like some of the early '80s SSPs I've seen. Should I just go with the painted 10-holes?
By David Freiburger
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!