What are the downsides to using a thick head gasket. Long story short, I needed to replace my pistons. I have 64cc Indy SR heads on a 500" B block and want to get my compression down to 10:1. The piston manufacturers are saying with a 1009 fel pro, there is no way to get the compression down that low and retain strength in the piston itself. So the question is about going to a thicker head gasket. Are there any significant downsides?