heli-coil

That is the key to a heli coil job. Drill and tap straight. I just got a intake with 2 heli coiled carb holes. While the work done on them is fine enuff, the angle is slightly off on one hole. It's not a problem, you just can not tighten the carb stud down until the carb is on. The slight tilt is very very minimal and getting the gasket and carb on require the stud to be a 1/2 turn loose.

Once on, the final 1/2 turn isn't needed since 99% of the threads are engauged.