Quote:
Originally Posted by qmdv
Lets start with what I know about the engine: My dad bought it 50 or so years ago. 59AB, bored to 3 5/16, 4" crank, Offenhauser 375 heads and 2 97's. It sat for many years and I went through it. Cylinder walls rough so I went 30 over and put it in a 32 Hi Boy roadster. Unfortunately I did not check head volume while engine was opened up.
Now for the problem at hand. I put 87 non Ethanol gas in it and it rattled terrible. Drained the gas and put in some 100LL aviation fuel. Man it ran great and sounded great. So I drained out that gas and put in some 91 non eth gas and if I really get into it in high gear I get just a little detonation.
So what are my choices? I can just drive conservatively but now and then I like to put my foot in it. Maybe bight the bullet and get new heads.
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I should first establish your piston to head clearance. Then go from there aiming for 40 to 50 thou clearance. You may be able to work existing heads to suit your set up. And also maybe establish your cc volume at combuston space as some deads are 64 cc and others at 75cc another area for you to work with. Dont continue driving as from experience detonation can screw up your engine big time. I have been there .
All the best Phil