When I disassembled my motor, one of the head bolts came out with about 3/4" of the aluminum threads from the jug. The only Helicoils I can find are only 12mm long (M8x125). The treads in the jug are about 21-22mm. Do you think that the 12mm helicoil is enough to hold the head bolt? If not...is it possible to insert two helicoils in the same hole?