helicoil in heads

Not too sure what holes your talking about. The three closest to the headers should be no problem. The two closest to the intake have extra meat on the bottom that are visible in the intake port. If you drill and tapp these to a larger size for the heli coil you might break threw then you need to putty(moroso) up the area so you don't suck oil in. It would be best to do with the heads off but I've had great luck with someone holding a shop vac right next to the bit and tapp. Hope this helps.