Big Block Chevy
 

I have a BBC casting number 3963512 dated C-26-71 has TKA id that should be out of a truck it is a 4.125 bore bottom of the cylinders are notched for a 4.00 crank has anyone ever ran across this before just curious?

Re: Big Block Chevy
 

Hey Buddy!

That block should be 4.250 bore. They never put a 4 inch crank in anything else.
Is it a 2 bolt block?

Re: Big Block Chevy
 

A 1971 512 block should be a 454 with either 2 or 4 bolt mains, may have a steel 454 crank. There is however a possibility that it was a 427 service replacement engine, but both the 454 and 427 were 4.250" bore. If it truly has a 4.125" (402) bore it is rare indeed, and it is possible, if highly improbable. Good old block, I like finding them.

Re: Big Block Chevy
 

2 bolt block, ive bought and sold several of these things over the years and even blew a couple up but never saw a 4.125 bore. Also never read anything printed in black and white that this was ever made. DAMNFINO

Re: Big Block Chevy
 

If it is a 1971 402 truck engine Pull the heads. They have an interesting chamber that is smaller than it looks. I think the rod bolt cutouts are a casting thing that are on all BB Chevies after the 427 faded in 1969. (went to 454 4" stroke)

Re: Big Block Chevy
 

I'm gonna look at my 402 blocks and see if any of them have the rod notches at the bottom of the jugs, but I never remember ever seeing that.
Alan, Adger, think we might have a canadian block here?

Re: Big Block Chevy
 

Sounds like they had to use some 454 blocks to make 402 truck engines. It wouldn't surprise me terribly. Yes, it is common to see the notches in post 1969 blocks, when the 454 replaced the 427. The 512 block actually was the basis for both the 68/69 427 and the 70 and later 454. That's just from the casting dates I've seen personally on stuff I know was unmolested.

Re: Big Block Chevy
 

If it is a 4.125 bore, I suspect you have pretty thick cylinder walls.
It is a good canidate for a 396/402 stocker application.
But, who would build one now considering the current state of the sport.