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in theory both identical, the CAST IRON (nobody makes cast steel heads) would make more power due to slower head dissipation.

that said, one of the performance mags tested the theory on a SBC using some dart or AFR heads that ARE identical except for material, and guess what....they essentially made the same power.

I'd go aluminum for the weight savings/repairability aspect, unless the iron was significantly cheaper.

kinda moot though, as the only heads I know of that are essentially identical except for material are the indy S/R's that can be had in either iron or aluminum....

you can run more compression on aluminum heads becasue the higher heat dissipation helps reduce detonation.

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The iron heads will make more power with all things being equal, just like the block. Aluminum expands eight times more than cast iron so the compression does goes down as the motor warms up, the heat loss from the aluminum is another contributing factor also to the totaal power loss

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kinda moot though, as the only heads I know of that are essentially identical except for material are the indy S/R's that can be had in either iron or aluminum....

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kinda moot though, as the only heads I know of that are essentially identical except for material are the indy S/R's that can be had in either iron or aluminum....

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I think it's only the 440-1 indy makes in alum and Iron .

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I will tell you where i am going with this. i have 2 motors apart now from 2 of my cars. one is a 340 the other is a 360.
I want the better running one to go in my 70 dart and the other in the car i drive more regularly.
the 340 has 10.5-1 forged pistons, with the eddy aluminum rpm heads it comes to 10.3-1 , not sure what it would be exactly with the factory j heads but it should be close to the same.
the 360 has hypertecnic pistons and a cast crank. with factory heads it should be around 8.8-1, with the edy rpm heads it should be around 9.3-1.
so i was thinking the 340 should run better than the 360. i still need to chose a cam yet . but the iron heads on the 340 almost make the compression to high for pump gas. that and i wonder how much good the heads would do on the lower compression 360 anyway. I thought that the 360 would run fine on pump gas with the iron heads but not the 340. in my head it would seem that the eddy heads would be better off on the 340 with a good cam. but what do you think?

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here's a link to previous discussion of this subject, except that I was (and still am) more interested if there is an efficiency loss when using aluminum heads:

https://board.moparts.org/ubbthreads/show...rue#Post2782669

in a nutshell,
what I found was that there does not seem to be an efficiency hit from using aluminum cylinder heads with their higher thermal conductivity, despite what you may commonly hear.

the best article from that previous discussion was:
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Car Craft magazine has put this technical article up
on the subject of Aluminum versus Iron cylinder heads:

http://www.carcraft.com/techarticles/ccrp_0602_iron_versus_aluminum_cylinder_heads_test/index.html

sample quote:

"Can you guess what we learned? Zilcho. As in zero difference anywhere in the power or detonation characteristics of the iron versus aluminum heads. Even the optimum total ignition timing was the same at 36 degrees. Regardless of coolant temp, rate of acceleration, steady state, or through a sweep, the dyno curves for the two styles of heads were identical. If anything, we could squint and guess and mumble that maybe aluminum heads were better by 2-3 hp. But the one thing we could never say is that the iron heads retained more heat and made more power than the aluminum. Maybe it's different on some engines with a drastically different water-jacket design, but we'll stand up and say that the old bench-racing line just ain't true."

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