I seem to remember a show or an article someplace that did dyno testing and put that belief to bed and proved that wrong. I don't buy that at all.

 

Cast iron heads can actually deliver more power than comparable aluminum heads because cast iron can retain heat as opposed to aluminum, which dissipates the heat. The more heat in a combustion chamber means a higher potential for power.

However, The lighter weight of aluminum pays big dividends in performance, so the bottom line that cars equipped with aluminum heads can accelerate comparably, even with less HP.

 

Here is a great artical to read and does somewhat prove what I said about steel casting heads.

Steel VS Alum Heads[sm=bustedsign.gif]

 

Many people don't pay attention to the compression ratio when going from cast iron to aluminum heads. Fact is that if everything was equal the cast iron head will make more power than an aluminum head. This is because the cast iron head doesn't absorb heat from the combustion process as fast at the aluminum head. Therefore more heat is available to push the piston down. The way to get back the lost horsepower is to up the compression on the aluminum head. Typically you can run about a half to full point more compression with an aluminum head over the cast iron.