BTW.... If you had an accurate steady state dyno, and the AL was actually pulling out more heat to keep the chamber temps lower, then the coolant temps wold rise.
More heat into the coolant would mean more fuel burned too. OEM's all using aluminum heads suggests that there must be other reasons to use aluminum (hint: it's cost and weight savings).
True, cooler at the start will be far less prone to preignition - that's a fact.
The question then is whether the air coming into the chamber is a different temperature than if the head were made from iron. In a water cooled engine there's going to be little difference. I would argue the exhaust valve has more effect on charge temperature than the chamber itself (still trying to find the ASME paper on the subject), and that an aluminum head cools the exhaust valve slightly better but not enough to have a tremendous impact on compression ratio choices.
