Stripped Holes in Cylinder Head for Intake Manifold Bolts

Using a hand drill in my opinion is a bad idea, you can get an oversized hole real quick cause you are drilling with the outside edges of the drill and you can’t hold the hand drill steady enough. Better to do it on a drill press and best of all on a milling machine with head clamped down.

Helicoils are hardened and are a stronger thread than than the holes in the head now. Plus the hole and helicoil tap will produce a smaller hole than the next size up.

And **** metric anything.