Re: Aluminum vs. Iron: Apples-to-Apples
For what it's worth, back in the '70's, before everybody started manufacturing aftermarket heads, there was quite a bit of testing done comparing the open chamber Big Block Chevy Aluminum Square Port Heads with the Cast Iron Square Port Heads. Both were over the counter items.
Out of the box, the Iron Heads always made a little more power. Everybody attributed it to the better heat retention of the Iron Head. On a flow bench, the Iron Head's square Exaust Ports flowed better than the Aluminum Head's Round Ports. That could have had something to do with it as well.
I ran both on my APBA Super Stock Race Boats. In that class, you could do absolutely nothing to the ports, just a "competition valve job" as described in the rule book. Honestly, I could not tell much difference in the RPM at top end.
Anecdotal at best. But all all things being equal, I preferred the Iron Heads. There were simply too many problems with the Aluminum Winter Casting Heads to justify the weight saving.
Of course, things are different now. Modern aftermarket heads are light years ahead of those old Chevy Aluminum items.
'67 Chevelle Malibu, Catalina Blue, 540 inch Rat, Air Flow Reasearch 290 CNC Heads heads, Custom Hyd Roller, .675 lift, 234, 244 at .050, Lemons Headers, Holley Multiport Fuel Injection, TCI 6X 6Speed Automatic, 12 bolt Posi Eaton TruTrac, 3:31 Richmond Gears, front and rear power disc brakes, Global West Suspension, etc.
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