Alloy heads

Tinmannz said
My understanding is that because heat is a major component of detonation and aluminum dissapates heat better than cast iron, this makes them less prone to detonation.
If all things were equal, an engine with aluminum heads would be less effective due to the loss of thermal energy. Cast iron is better at heat retention and keeps the fire in the hole longer whereas aluminum absorbs and dissapates the heat. Perhaps this is why you can bump up the compression with aluminum and retain some heat for the combustion process, putting that heat back in the hole where it belongs and not losing it through absorbtion.

Tinmannz statement above is pretty much the long and short of it. His statement is accurate. Ten years ago I wouldn't have believed that an aluminum head would tolerate more compression than an iron head but it will. Aluminum will suck so much heat energy out of the combustion process it will cause a negative effect on cylinder pressure. Pressure = power. How?

I'm only going to write this once and it is amazing how few truly understand how the force to push against the piston is created. It's heat and the more of it the more pressure. It's not and explosion it is a burn. Air and fuel enter the combustion chamber, the piston squeezes the mixture which helps the heating process, the sparkplug ignites the mixture and the mixture burns which causes the rapid expansion of Nitrogen. It is this rapid expansion of Nitrogen that works against the piston crown. Aluminum can and will reduce the amount of thermal energy available all other things being equal.

Anyone that's ever TIG welded on an aluminum cylinder head would notice that you have to stand on the pedal to get your puddle going but once the head heats up and gets too hot too touch it takes very little amps to produce a nice puddle. This is because aluminum wicks heat energy away like crazy. Same thing in the combustion process. Anyone that argues this is not speaking from experience and lacks critical thinking. J.Rob