I have a friend who has an 89 Firebird 5.7 w/tpi and a Vortech and he has the stock cast iron heads. (No casting #) and we are trying to determine what the stock head combustion chamber volume is. He wants to go to aluminum heads and drop his compression to 8.0-8.5 to one range. Anyone know what the stock cast iron L98 F-Body app combustion chamber CC's are? Thanks. Mark