Octane
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Instructor
Joined: Apr 2010
Posts: 185
Likes: 8
From: Gilbert Arizona
Just how far along is your motor? Nobody here has mentioned aluminum heads. Aluminum dissipates heat faster and you can run with higher compression. I assume you would be paying for a head rebuild so that is a $$ trade against new heads.
Don't remember my SBC spec's but the switch to aluminum let me run with 91 here in CA for years and years. Also there is static and dynamic compression which would depend on your cam timing. I am not a motor builder of any kind, just mentioning more topics that may be of value for you to research. And yes, stay away from dished pistons whatever you do, bad experience there, not cheap to unwind that decision.
My LS7 CR is 11:1 and 93 is recommended but I can only get 91. Runs fine, but of course it has knock sensors, so who knows what's going on. But my experience sort of suggests 10.5:1 would be OK.
Don't remember my SBC spec's but the switch to aluminum let me run with 91 here in CA for years and years. Also there is static and dynamic compression which would depend on your cam timing. I am not a motor builder of any kind, just mentioning more topics that may be of value for you to research. And yes, stay away from dished pistons whatever you do, bad experience there, not cheap to unwind that decision.
My LS7 CR is 11:1 and 93 is recommended but I can only get 91. Runs fine, but of course it has knock sensors, so who knows what's going on. But my experience sort of suggests 10.5:1 would be OK.
It's completely torn down now
Safety Car
Joined: May 2004
Posts: 4,347
Likes: 1,576
From: los altos hills california
Just to update my post to actuals, I went back through my 2002 records. My heads are Pro Topline 72 cc chamber volume, 3.75 stroke, -5 cc flat top pistons, bored 40 over. CR looks to be about 10.3 and as I mentioned 91 is the best gas available here. Pretty safe combo, ran it hard for 10 years, never an issue even on the hottest days, sitting in a line getting ready to run.
