I have a stock 1972 455 with j heads and would like to up the comp ratio, what is the thinnest head gasket I can run.

 

Well, it's already got a gasket that's about 0.016". I doubt you can get any thinner than that.

- Eric

 

Welcome. FYI, J heads are from the 1973-76 model years, so your engine is not "stock" and has been apart at some time previously. Since the heads have been off, chances are your engine no longer has the original 0.016" head gaskets and more likely has thicker aftermarket gaskets, probably 0.040". Frankly, given the soup bowl-sized dishes in your stock pistons, changing head gaskets will provide a minimal CR change that is unlikely to be noticeable when driving.