Heavy Z Posted December 16, 2003 Share Posted December 16, 2003 Can someone who knows more about this please explain - I've read many times on this site about the fact that aluminum heads can take compression better than iron heads. Why? Thanks Quote Link to comment Share on other sites More sharing options...
fl327 Posted December 16, 2003 Share Posted December 16, 2003 heat dissapation properties are different between the two. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted December 16, 2003 Share Posted December 16, 2003 Aluminum absorbs heat quicker so detonation becomes less prone. Aluminum also sheds the heat much quicker. Try it at home with a piece of aluminum and a piece of iron. Heat them up the same amount of time, see which one is hotter. Come back 5 minutes later and see which one is cooler Tim Quote Link to comment Share on other sites More sharing options...
Heavy Z Posted December 16, 2003 Author Share Posted December 16, 2003 Thanks, is there a ballpark figure on how much more compression they'll tollerate compared to iron heads? Something like "you can run 10:1 with iron heads and 10.5:1 with aluminum heads on 91 octane gas." You probably get my drift. If there's an answer, thanks in advance. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted December 16, 2003 Share Posted December 16, 2003 There really is no rule of thumb because so many other things affect compression ratio, like cam especially. But IF you wanted to put numbers on it, I would say: 11.5:1 with ally heads 10:1 with Iron heads. Again, depends on altitude, fuel, ambient air temp, ignition system etc etc etc..... Tim Quote Link to comment Share on other sites More sharing options...
Pyro Posted December 16, 2003 Share Posted December 16, 2003 And.... With all things equal (chamber design, valve diameter, flow numbers, etc.) iron heads will make more power than alum. heads at compression ratios lower than about 9.5:1. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted December 16, 2003 Share Posted December 16, 2003 And....With all things equal (chamber design' date=' valve diameter, flow numbers, etc.) iron heads will make more power than alum. heads at compression ratios lower than about 9.5:1.[/quote'] That seems to directly contradict what was explained above. How can you explain iron heads make more power at less than 9.5:1 compression? Quote Link to comment Share on other sites More sharing options...
Pyro Posted December 16, 2003 Share Posted December 16, 2003 More heat in the combustion chamber. Less heat loss allows more work to be done. Quote Link to comment Share on other sites More sharing options...
Guest zfan Posted December 16, 2003 Share Posted December 16, 2003 Iron heads make slightly more power than aluminum. Super Chevy did testing and compared several different heads. Mike Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted December 16, 2003 Share Posted December 16, 2003 Here we go again with the "all things being equal." Yes, if "all things are exactly the same" the iron head will help to generate a little (and it's very little) more power because of reduced heat transfer. However, aluminum heads enable a higher compression ratio and therefore, will generate more power. Quote Link to comment Share on other sites More sharing options...
Guest AJ78 Posted December 18, 2003 Share Posted December 18, 2003 Here we go again with the "all things being equal." Yes, if "all things are exactly the same" the iron head will help to generate a little (and it's very little) more power because of reduced heat transfer. However, aluminum heads enable a higher compression ratio and therefore, will generate more power. And they will be lighter! Quote Link to comment Share on other sites More sharing options...
Guest BigWhyteDude Posted December 18, 2003 Share Posted December 18, 2003 so in real world conditions the Aluminum heads are better for high HP engines??? Andrew Quote Link to comment Share on other sites More sharing options...
Z8 Posted December 19, 2003 Share Posted December 19, 2003 In my opinion, and experience (for whatever that's worth) in "real world" conditions and outside of wide variations in specifications, the only significant difference is the 35 lbs. of weight. A good iron head can make great horsepower and hold a high compression same for a good aluminum head. There are differences of course, but an iron head that has been ported, flowed, good valve train, etc. will make all the HP you need. I've built engines both ways. Quote Link to comment Share on other sites More sharing options...
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