97-13 LS heads : LQ4, LQ9, LS1, LS2, LS3, LS7. 92-97 LT1 Chevy Heads. This kit will repair stripped holes in your cylinder head for M14 threaded spark plugs (See common applications below). The way this works is that you will start to thread the tap into the hole, which then widens and threads the hole larger than before.