Quote:
Originally Posted by 1969GPSJ
Nope, the 16 casting heads I have cc'd have been consistently right around 72 ccs (low end 68 ccs, high end 74 ccs, but the low end may have had been resurfaced). Pontiac was pretty good with the RAIII and HO "d" port chamber machining consistency. Post 1970 heads may have had larger chambers, but the '68 through '1970 open chamber high compression D port heads used on the performance 428s and 400s did not.
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Are you running pump gas now ? Or you mixing it. I had 69 Grand Prix 428, and never had a issue with runing 93 octane pump gas.