Fred, castings continue to normalize over their life. Jerry made the point that it's usually only a few thousands. Bridgeport Milling machine base castings used to lay out in the field for two years before they were stable enough to bring them in and start the machining on them. Blocks and head are almost always warped up a little over the specs when down for a rebuild. Line boring is as common as decking, head milling or crank straightening and again is very often due simply to the castings normalizing. We tend to think that iron/steel is absolutely stable material and that it doesn't move around but like all materials it is plastic to some degree. When you subject the structure to cyclic heat and vibration it wants to eventfully settle into a relaxed state, aka, warp.
Denny Graham
Sandwich, IL
