A friend of mine is looking at getting an 86 Iroc. It has the LB9, 305 TPI engine. The engine has a bad head gasket, and to get some more power out of it we are thinking of putting in a thinner gasket. In another thread I read about using a FPP-1094 Shim, and that it is a .17 thickness, compared to the stock .32. How much will this raise the compression in this engine. It has the original heads on it, 58cc. Another problem is that this block is already a .030 overbore. Will this head gasket work on this engine. Won't the size of the hole for the piston in the gasket be wrong? What other gaskets would you guys suggest to raise the compression a little bit?

 

That shim is not gonna be a good thing. Consider: the original head gasket blew out. A thinner gasket will have less sealing power than a regular gasket (less material to conform to the surface irregularities.) So what are the odds that the thin gasket will hold where the thicker one failed? Not very high.....