Just a quick point. I've used Helicoils in spark plug holes and it is fine for shopping carts but if you are going WOT regularly fit a solid insert. I found out to the detriment of an engine that Helicoils don't/can't transmit a lot of heat. The solid inserts actually dissipate heat better than spark plug straight into Ali. Don't use anything,(Loctite), on inserts. On spark plug threads Champion and other manufacturers recommend Graphite powder but Nickle-coat anti-seize works too.