When someone talks about heads and runs through the "numbers" on a particular set of heads, and then finishes up with "they probably 'FLOW' about 275" what do they mean by flow? and 275 what? Also, besides obvious combustion chamber volume, what is the difference between 64cc and 72cc heads... ie: how do you decide which heads you'd prefer? Peace

FLOW refers to how much air flows through the head at a given pressure. There is a flow number for the intake and one for the exhaust side of the head. Flow is usually measured in cfm (cubic feet per minute). As for what combustion chamber size to use, that depends on what kind of compression you want and is determined by your piston/rod combo and deck height. Lower combustion chamber volume = higher compression for a given piston.

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ThaDex
1981 Z28
1978 LT