New aluminum heads ain't cheap. I would let them do a thread relacement for that plug. Not a helicoil, but a full thread replacement. Thread inserts are just that. They drill and tap a bigger hole then replace it with a hardened insert. Helicoil's I have seen in kits are thinner and softer than a thread replacement. Plus, if a good mechanic does the job and secures the insert properly, you shouldn't have any issues. This is just my opinion about thread replacement on industrial machines, not aluminum heads. I've never replaced any threads on anything aluminum. But they will have to pull the head and do that work, I would think. Geez I would hate to blow a plug out. You must have been gagging her pretty hard??
