1slo_camaro

iTrader: (2)

i was told by someone that iron flowed better then alum. stock for stock. can someone please clarify this for me and show some evidence please

Mighty Whitey

that seems to be the info I've got. basically for the reason that a thinner iron casting will hold up better than a comparably thick aluminum piece.

why a 3/8plate of steel is probably as strong as a 3/4 plate of aluminum.

COPO9560

Assuming the heads are ported the same, flow should be the same as well. The key difference between iron and aluminum is heat transfer out of combustion chamber. Aluminum transfers heat out much faster, resulting in less combustion temperature and pressure. Not a big difference but on older engines you should increase compression ratio when moving to aluminum to maintain same power. Aluminum blocks can have a similar impact.

danhr

iTrader: (18)

I believe the OP is more specifically comparing the lt1 iron heads to the aluminum lt1 heads.

IIRC, the iron heads flow about on par with unported 561 heads, and they flow better than unported 653's.

The 653's have a lot more meat to port though, and are more sought after by head porters.

96capricemgr

iTrader: (1)

Basically the iron heads were designed a couple years after the early aluminum ones so they had the advantage of a little more R&D, in 96 the aluminum heads fiaally flowed asmuch as the irons BUT are a thin undesirable casting.

For porting the 95 and earlier aluminum heads are most desirable despite the fact they flow the least as cast.

If the irons are heavily ported they can crack since cast iron is more brittle than aluminum, seen a few guys have trouble with this, not a lot but a few.

http://www.fierolt1.com/lt1_lt4_headflow.htm

99 Black Bird T/A

iTrader: (4)

It's my understanding the Aluminum LT1 heads were designed first. The Iron ones spent a little more time in development and stock vs stock have slightly better airflow.

Taubr Unit

iTrader: (32)

good to know i have the better heads to port for stockers

GIZMO

iTrader: (8)

Sorry guys, but I have flowed quite a few sets of bone stock aluminum LT1 heads and the 1996-97 561's are by far the worst.

malibuwagon

The reason alum lt1 heads where on the hi po engines was that u can run higher compression without detonation...so more power Jim

96capricemgr

iTrader: (1)

GIZMO, first I have heard that, but I trust you over most sources.

malibuwagon I think you are oversimplifying things with 60s era mentality.

GIZMO

iTrader: (8)

Believe me, I was highly disappointed after spending $1,500.00 to blueprint a set of $400.00 heads that slowed my car down! I actually went out and purchased more just to see if I had a "bad" set. None were as good as the earlier castings. If someone has actually flowed a "good" set, please post your results. The late model intakes are an upgrade over the 1994-95 intakes (don't expect a big gain).