-Iron heads off of a 1968 GTO"
There's your problem. Too much compression! To verify, get your tank almost empty and put in 5 gallons of 110 octane race gas, drive it for awhile, and then tell us how it runs. The only solutions that I see are, dished pistons or heads with larger combustion chambers. That is, probably, part of your temperature problem, too. pump gas and compression just don't mix!
Last edited by WDCreech; 08-06-2009 at 02:25 AM.