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Originally Posted by slowbird
It is interesting that Jon got alot more flow out of his 1.72 exhaust valve than the as cast head does with a 1.80 valve. Also Jon really picked up the intake flow. The as cast number from AllPontiacs web site list them as in/ex .500 318/211 .600 360/233 .700 386/249 .800 399/262. Averaging the number Jon got 397.75 for his intake compared to as cast 365.75 and the exhaust Jon got 267 compared to 238. Also from what I have read the as cast port volume is 310cc and in the DCI post he said that Jon intake port volume was 310cc. Just wondering how that can be right unless the as cast port volume has changed. Anyway it looks like they are killer heads.
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What size bore did he use when testing his heads? Perhaps a larger bore than All Pontiac used. The 37cc combustion chamber might have something to do with it as well. Guess you could mill the intake surface some to reduce the volume increased if you needed to stay within certain rules. I'm not sure what the restrictions were.