[RahX]

They call it torque to yield and should be replaced every time. It can take just one overheat to warp a head. USUALLY it takes quite a bit to warp the deck of the block. It is always a good idea to have the head checked since it could be anything from a warped head to a crack in the head. If it is just a matter of machining the head, make sure if they go over .010" to get a copper head gasket shim of the thickness machined away so you don't run into problems with the timing belt/valve train.