can anybody tell me the factory pistons dish and or valve reliefs in cc's for a 90 l98? also how far down in the bore is the piston at tdc? This is in a stock 90 GTA. I'm trying to calculate my compression ratio and need that info.

 

you really need to measure it since there is varations in the parts and machining process. good guess is 4 to 6 cc and .020 to .030 in the hole.

 

Thanks for the info ede. I guessed the reliefs were about that but .020 to .030 seems like it would be way too far down. The trick flows I'm going to use have the same 64 cc chamber as my stock heads but I want to use a felpro 1094 head gasket for a little more compression. I guess I'll have to wait until I get the old heads off. I've also thought about having that heads milled but that might have to wait.