New heads?

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I agree starting with rumbles first post
what pistons
what quench
what compression
all the other build details
not even close to be able to make a head suggestion
too big a head and he could run worse for his application
 
I agree starting with rumbles first post
what pistons
what quench
what compression
all the other build details
not even close to be able to make a head suggestion
too big a head and he could run worse for his application
Thank you very much. I believe MPOffical I s good hearted and means well for all as well think he is a “Good Fella.” But I think the lack of information & the correction of it is the key to start with.
 
FWIW and IMHO..... The above 2 posts are apples and oranges.
  • Hotter iron chambers make more cylinder pressure inside (prior to the start of combustion)? Yes. But that value of cylinder pressure is not 'compression ratio'. It reflects both compression heating, AND the absorption of heat from the chambers, which are 2 independent contributors to the heating of the mixture.
  • The effects of cylinder pressure on torque/HP all depends on the difference between the starting and ending pressure during the combustion and power stroke cycles, not by the absolute numbers themselves.
  • More HP? Not just based on a different cylinder pressure (piror to combustion) by itself. I agree, I've looked and looked for definitive results showing a difference going from iron to AL and have found none published; the trick in such testing is to always make the other factors identical.
  • BTW, RF, your positive experience with the head swap does not zero in on the exact cause of the difference you found unless you flowed both heads and found them identical. I'd guess you got some benefit from flow (but that is truly a guess); but you certainly got some benefit from more efficient combustion (partly from the higher CR, and partly from the smaller chambers), better cylinder clearing, and better extraction of power at the higher CR due to a bigger start-to-end pressure difference.)
I'd change AJ's statement to say that, rather than 'curing' anything, the cooler AL heads ALLOWS more CR without getting into detonation. AL heads widen up the operating range for CR and cam selection by reducing an undesired factor in the engine operation (extra mixture heating during compression).
I think your smart and smarter than most. I’m not just going To Engage in splitting hairs on a post half way to sideways on a combination that is unknown.

But I get where your coming from and agree with the thinking.

The biggest problem after or before not knowing the op’s Combo is the most tended use and what is acceptable for him in terms of cost or performance from, where is it he stands now?

385 HP cam he had in a few different ways.
Big cam, stock-ish lightly worked on heads
Med. cam ported heads
Small-ish cam but well ported heads on a well thought out working efficient combo

Still! Looking forward to this thread. Great minds at work here.
 
I agree starting with rumbles first post
what pistons
what quench
what compression
all the other build details
not even close to be able to make a head suggestion
too big a head and he could run worse for his application
It's a .030 360... how many stock replacement heads out there do they make that could be too big ? Lmfao.
W series, trick flow, anything "too big" wouldnt be stock replacement.

They're too small from the factory, edelbrocks are bigger but still smallish, not saying that's a bad thing...at all...theres always 2 sides though, anyhow.. it would be damn hard to make a set of factory 360 heads too big for a 360 aiming for 425hp.

Buy heads or port heads 'or do both' , iron or aluminum...your choice.

Just get your monies worth. Good luck.
 
Thanks everyone for the replies I’ll try and add more info to my original post. Comp cam 268, Keith black 107 pistons, 10.5-1 compression, eddy airgap intake, Hedman fenderwell headers. Holley 750. Hope this helps.
 
Thanks everyone for the replies I’ll try and add more info to my original post. Comp cam 268, Keith black 107 pistons, 10.5-1 compression, eddy airgap intake, Hedman fenderwell headers. Holley 750. Hope this helps.

I assumed as much, the cam is ok'ish...small... and with those numbers its saying the heads aren't doing much for flow.
Post flow numbers, if you have any... if not, that explains the type of port work that's been done.... gasket match, sand paper roll and probably going turbulent at .450+ lift and flowing backwards.

I made 392hp with vj'd stock x heads on a 340 and a 280 duration .500 lift cam...that should be an indicator right there of what your heads are doing, which is squat.
 
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