Originally Posted by Techno Duck

Just curious, do most cylinder heads removed from our cars need to be resurfaced due to some small but measurable warping? I had my cylidner (with about 85k miles on it) head checked at a machine shop and instructed them to do whatever was needed to make it perfect (new valve guides, 5 angle valve job and check for flatness). They told me the mating surface was perfectly flat and required no milling. I was surprised it didnt need any.