I took my om617.951 to a local machine shop in preparation for a rebuild. They called asking about a "ball bearing" in the back of the block and whether or should be removed before they clean the block. I believe it is pressed in and is an oil galley passage or something of the sort. Anyone have any clue what should be done? Can the ball be removed? Reused? Are new ones available? Should I tell them to ignore it and just go ahead? Thanks in advance for the help!