Cylinder heads
 

is their a performance difference between iron and aluminum heads other than the fact of aluminum being lighter and able to dissipate heat better?

You can run slightly more compression with aluminum heads without detonation.

aluminum heads
 

aluminum heads are better in many ways generaly they have much better port designs because they dont have to be limited by the water jacket as they do in factory cast iron heads not to mention the heat transfer aspect that is why you have to run higher compression with aluminum heads because it makes for a cooler more dense cylinder charge which actually drops cylinder pressure

The only real performance difference is that aluminum heads are lighter. It's really a toss-up of which is better...loosing weight or loosing heat in the cylinder.

Ideal, you want as much as a cold intake charge as you can get going into the cylinder...stuff as much air in there as possible. However, once the intake valve closes...if you could create as much heat and compression as possible...and keep it all in the cylinder you would see some pretty wild cylinder pressure.

Think of it this way...if you throw an aerosol can on the ground..it does nothing:( , but if you throw it in a fire...it takes off:)

Murdock