Mopar Action SB head article

Aluminum is used because it is lighter, easier to modify, and easily repairable. But in order to get the utmost out of them, the engine needs to be built to take advantage without giving up too much to disadvantage. If the race teams could have an iron head that is light, they'd use it. In fact, it can be argued that the use of thermal coating on the chamber basically duplicates the properties of iron in terms of thermal efficiency.