As I understand the heads on 68-71 350 engines are the same, true or false? What is the comp. ratio on my -68PP engine (assuming stock type pistons) And if so, what is the difference from the 10,25? -70-71 350 Lars
69-70 engines are 10.25:1 CR, and the heads have a 48 cc chamber. The 71 and up heads sre 50cc. Your engine should be 10.25:1
compression ratio According to my info the '68-70 4bbl engines have 10.25-1 and the 2bbl engines have 9.5-1. my$.02
10,25:1 Thanks! :beer With 10,25:1 there is no reason to mill/cut the heads, is there? I do NOT want to use any octane booster. Lars
Don, you may be correct on that. Not sure about 2bbl engines. Lars, keep in mind that is advertised CR not actual. Actual is probrably about 9.5:1. You should be good with your setup.
Re: 10,25:1 To help get the most out of your combo and to help minimize the chance of detonation...you will most likely need to have the block decked. You want to wind up with a piston-to-head clearance between .038"-.044". How much you have decked, depends on which head gasket you use. If you go with a composite gasket - that should give a compressed height of .038" - have the block decked between .005" in the hole, to zero deck. If you use the steel shim gasket, the machine shop will need to adjust accordingly. I believe that the steel shim gasket is about .015" or .018". The idea is to get the 'quench' as tight as possible. That squeezes the mixture into the center of the combustion chamber, minimizing the possibility of detonation.:TU:
Thank you boys! Thanks :beer The next time i take my babe out (the 350 that is). She is going to have some deck job done. :bglasses: Lars
I agree, I had my 350 decked .050, that put the piston only .005 in the hole. I have no problems running on 92 to 94 octane gas:beer Mark
