Did you follow the factory service manual procedure for checking the block and head for warping?
It sounds like this is a basic fix it and go, but after the troubles you have had, I'd suggest doing it the way most shops do; send the head out to be pressure checked, checked for warping (yeah, it never got hot) and have the shop check your valve job. Stuff like what you have run into is why every aluminum OHC head gets sent out before bolting it back on.