Hello Everyone,
I've been thinking of the best and most economical way to bump the compression on my 427 motor. Right now my compression is around 10.9:1 with a DCR of about 7.8:1. I've been debating on replacing my pistons with some high-compression LS7 pistons from Diamond, but replacing the pistons just seems to be too much of a task for me. So, I thought about getting the chambers welded on my LS7 heads from their 72cc to 64-65cc's to bump the compression up to 12.0-12.2:1 and my DCR up to 8.5-8.7:1 with the cam that I have currently and getting my quench down to .030". Plus this would be FAR cheaper then getting the pistons replaced as I would be able to do the wrenching myself.
Does anyone have a good recommendation of a shop that can do this? Patriot Performance or WCCH, etc? Would doing this cause any problems, durablity? Would it be better to just get the higher compression pistons? or is it alright to do what I'm thinking or are there some serious negative effects? I know a lot of high compression C5R engines have most of the cc volume in the pistons (deep dish pistons with 32cc heads), so I thought that this would be ok to do.

Thanks in advance,
Adrian Mejia

 

I thought factory LS7 heads were 70cc chambers???

 

There is actually a variance in the head chambers for some reason, my GM LS7 heads have 72cc chambers, they were poured, so who knows what GM was doing haha.

 

how about milling your heads .020 -.030 thou and use a thinner gasket ? then if that isn't enough you could advance your cam 2-4 *

 

Adrian, you have the 70cc heads and cannot go a thinner head gasket. You are at 11.3:1 compression right now. If you shaved the heads you could get 11.8:1..

 

Hey Dave!
How far out the deck are my pistons? I must have the wrong numbers when I calculated my SCR. I don't have the build sheet you gave me (still in Iraq). My brother is currently enjoying the awesome engine you built me. =D

Best Regards,
Adrian Mejia

 

Sounds like you have a lucky brother! Glad to hear the motor is working good, and I'll see when you get back!