Aluminum heads will alway's expand at a different rate than Iron,,,,There are Better gaskets these day's made for just that application,,,,another old trick in the machine shop was to bake the Aluminum head until it warps,,,and then,,resurface it,,,,,this is because aluminum has a memory,,,,when it is warped,,,it becomes Tempered,,,and once Tempered,,it is not likely ever to warp again.