jbotstein1

I have 9:1 pistons. Should I use a stock headgasket? Or do I go with one of these 2-3mm headgaskets that I keep reading about. Wouldn't that lower my CR even more? Thanks

Black Nugget

Jonathan, yes that will lower your compression significantly. With 9:1 compression pistons I would just put a stock head gasket on and call it a day!

A 1.8mm Cometic Headgasket will lower you to approximately 9.8:1 if I'm not mistaken. So adding a 2mm gasket ontop of already lower compression pistons - your compression will be way too low, in my opinion.

jbotstein1

That's what I figured. What are the negatives about too low a compression ratio?

Black Nugget

Off the top of my head - low power. If you have say, an 8:1 compression your car will be rather sluggish prior to reaching boost. Obviously once you reach boost things will turn around for you.

kane.s2k

It will have very little power pre-boost, take longer to spool the turbo, make less power all through the powerband, etc etc. 8:1 is very low unless you are looking for some really really big numbers on race gas.