Quote: Iron bb heads valve cover rails are not flat. They are not supposed to be. The threaded holes are not square to the surface, they are tipped toward the intake side of the engine on purpous, as are the bosses they are drilled into. I'm very supprized you were able to get bolts in at all. If you put a straight edge on the thread bosses and compare that height to the front and the rear rails, you wil find about 1/8" difference. Those covers were meant for aftermarket heads. All of the aftermarket heads I know of have flat valve cover rails.
