Have you ever tried the gapless rings from total seal? When you buy file fit rings do you file the rings for the top groove only or is the second groove a file fit also??? As a rule of thumb is'nt it true you allow about four thousandth's per inch of bore? so a 4" bore would need a ring gap of about 16 thousandth's???? Any idea what that .016" gap becomes at operating temp??? Thanks for the previous reply. Turbo6man