Re: Aluminum vs cast iron heads
 

I dont know this from personal experience but I have told by people I believe that if you just switch to aluminum heads, all things being equal (and dont up the compression ratio some) you may loose a little power. I am going to do this too but when I do, Im going from 119 cc heads to the 110 cc edelbrock heads. I believe its also true that you can run more compression with aluminum heads.

Maybe the big engine builders can comment on this.

Re: Aluminum vs cast iron heads
 

I forgot to mention that I think my engine builder had said that 1 pound of boost is equal to something like 50hp or so.

Re: Aluminum vs cast iron heads
 

I cant say that I have actual dyno numbers on this but I have built alot of motors, so this comes from my experiences. I have never heard of a loss of power just because you switched to aluminum heads. However, the later part is absolutly true. You can run higher compression with aluminum over cast iron heads. The reason is that aluminum is a great heat sink. It takes away more heat from the combustion than iron, so a higher compression is achievable. Now I am not saying you can run 11-1 compression just because you have aluminum heads, but I am sure you can safely go 1/2 point higher.

Re: Aluminum vs cast iron heads
 

That's exactly why the first part is true as well. ALL things being equal iron will make more power. Heat is energy, energy is power.

Now, to answer your question. In post #3, you said you want more reliability and are not really worried about more performance. In this case, without question, iron heads are the way to go. Period.

Heat expansion, water jackets, overheating is just about an automatic head gasket replacement, etc.

DAVE

Re: Aluminum vs cast iron heads
 

A 540 with a comp of 7.5 - 6lbs boost - 671 should not have melted a piston . The setup sounds conservative and not even close to being on the edge. Do you know why it melted ? Bad gas/fuel pressure - timing problem - or overheat ?

Re: Aluminum vs cast iron heads
 

my engine builder can not tell me...

Always ran 93 high octane fuel and he said it wasn't a fuel issue. I'm very very curious as well to why so much damage occured. I was sold the boat on the engines being conservative and had a lot of problems from the start of which some were with the engine. Bad comp and leak down, and leaking a lot of oil. Probably only really ran the boat 10 hours and it gernaded at 3800 rpm cruising. Also oil looked like water when first drained but had been changed when I got the boat. Connecting rod broke, heat marks on bearings of rods, took out oil pan and damaged piston next to it. Also supprisingly engine still turned over. Also metal shavings everywhere in engine. Did always have fuel pressure issues, but had woking gauges and always was watching. Problem with fuel was at higher rpm's when fuel was low. Also have cam timing info if that would help.