KIBBLEWHITE VALVE EXH 1.57505-17TC 20-20776Some Twin Cam heads using 7. 0mm valves may crack in the port end of the valve guide boss, These valves have . 005" oversize stems to re establish the correct valve stem to valve guide clearance if the head has cracked, Valve guides must be reamed honed to set correct clearance, the a valve job performed to ensure proper sealing, Oversize portion of the valve stem does not extend into the keeper groove area; OEM valve keepers can be used