Once ported, will both heads flow close the same, or can the iron head make bigger power numbers?
The iron heads do flow more than the aluminum heads. Roughly 220 CFM @ 0.5 inches lift, 28 inches water column for the aluminum heads and 230 CFM @ 0.5 lift and 28 inches water column for the iron heads. The only problem is that aluminum has a higher specific heat than iron and thusly allows you to run a higher CR without risk of detonation.
