GR8ONE68

As I've mentioned in a couple other posts, I'm in the research phase of building a 421ci LS Series. There are several ways to get there, the attached Excel spreadsheet shows 3 ways to get there. My question is, has anyone ever bored a 6.0 out to 4.095? I'd love to go that route, but I don't think it is feasable. If I were to have a block sonic tested, how much material is recommended to be left around the bore after boring? This is going to be a N/A motor. Are there any blocks that are known to have thicker cylinder walls than others, LQ4 vs LQ9 vs L96 for example? I know there are other CI's that I could shoot for, and are safer builds, but I am going to build a 421 for it. It's going to go into an '81-'87 G-Body Grand Prix. 421 was the original large displacement motor in the early Gran Prix's and that is what I want to build for nostalgic reasons. I'm going to put the '66 421 badges on it also. I'm probably going to end up with the 4.04" bore and 4.1" stroke. I'd feel better with the 4" stroke, for bore side loading reasons, but if I can't get there with a Vortec 6000 block, then I'll probably go with the 4.04/4.1 build. I'll probably try to find an L96 to get the 823 heads.

bthomas

iTrader: (1)

4.065 is commonly done to iron 6.0’s, but I can’t see .095” happening without a resleeve.
talk to Erik at hpr, he does a lot of the big stroke engines. He specs a different piston than what’s available off the shelf to get them to wear less.

BigDaddy97

I ran a 421 (4.030 bore x 4.125 stroke) in my S10 a few years back. Built it from a Lq4 block and it lasted hundreds of 1/4 mile passes.