Senior Tech Team
Join Date: Feb 2005
Location: Long Island, N.Y.
Aluminum vs. Iron: Apples-to-Apples
Recently had the opportunity to R&R a pair of iron heads and replace with aluminum. The block is an aftermarket iron.
Platform=BBC, 9.8:1(flat-top pistons), mech-roller, 100% pump-gas compatible.
Absolutely not giving ANY brands here, it is NOT about the mfr's! Both head choices are compatible with the sole exception of the material.
I'll call them heads "AL" and "CI", based on the material. Both sets were very close in runner size, not enough to have any major effect in the larger picture.
Here are the flow numbers for both sets.
Heads "AL", flow: 370/280 @ .700"
Heads "CI", flow: 375/270 @ .700"
Flow numbers for both pair throughout the entire lift range were very close. There was NO add'l extensive porting on either heads, some very simple bowl work and identical on both sets!
Unit made 795 HP/750T with the "iron" and 742 HP/725T with the "aluminum". We've been well aware of this difference between the material components for years now. Aside from our own previous testing this had come up in a long discussion with a "very-high-up" (owner) at Dart back when, mid '80's or so.
This is as close to a "true" test as we can report on, really not looking to get into any "deep" debates over this issue, "it is what it is", at least for us.
Thanks, Gary in N.Y.
P.S. Again, I'm NOT giving any head brands due to the fact it would have made absolutely no difference in our results, we really don't care about brands due to our own very highly experienced in-house head porter. We simply wanted both pairs of heads as close to identical as possible.