The Ford Triton Engine Insert Kit, No. 39300, from Mac Tools allows technicians to replace damaged spark plug threads without the expense of removing the engine head. After application, the custom designed insert becomes a permanent part of the engine. The new kit is compatible with three-valve, 5.4L and 6.8L Ford Triton engines built before Oct. 9, 2007 and with three-valve, 4.6L Ford Triton engines built before Nov. 30, 2007.