Nadelle

Twister

Aluminuim and Iron expand at different rates, iron a little more than aluminium. Plus aluminium sheds heat easier.

all that adds up.

plus to run the same octane with alumium heads your should UP the compresion about half a point, becouse of the heat tollerance of aluminium.

all in all, the same head but cast in alumium will run a little better than iron. BUT iron is a hellava lot cheaper


go with the GT40p heads, their cheap and plentifull

Twister

Don't want to get into an arguement here, but here is a Chbby test with heads that flow the same... http://www.chevyhiperformance.com/te..._engine_heads/
not much difference

P Zero

The GT-40's with minor port work will flow just fine to well over 350hp, if not more if you mill em a bit.
-P.

Nadelle

twister that article was inconclusive as wich has a performance andavtage.

"the two sets of heads were not identical enough to reveal the basic inherent advantage of the iron heads."

another point i didnt mention was that aluminium is alot lighter, that in itself will improve performance along with the other things i mentioned, better heat distribution, increased detonation tolerance givin the same compresion ratio, and less heat expansion should add up to aluminium heads flowing/performing better than iron.

I still think the iron gt40p heads are one of the best heads out there. I dont necisaraly think the advantages of auminium should make them so god damn expensive, thats why i almost always recomend the gt40/p irons for street use. as the iron cunstruction make them tuff as nails and cheap as dirt (affordable). the gt40's should yeild around 30-40 hp...not to shaby

but if you got the money and want every ounce of power you can possibly attain, than the pricey aluminium heads would prove more worthwhile.