The ring end gap should be checked and adjusted before installing therings on the pistons. Most piston rings are a little looser thanrequired so they don't require sizing, but you never know. The rule ofthumb is: .004-inch ring-gap clearance per inch of cylinder bore, whichcan vary with manufacturer. Piston ring sets that require file fittingfor all-out performance engines are available. File fitting piston ringsis tedious when done properly.