heli coil help

So you used the next size up bolt (which should be 3/8) and just tapped the existing hole bigger or what?

As long as it gets tight it will stay tight.

Here is some free advice from someone who has fixed more threaded holes than I care to even think about.

If it works, run it. If it doesn't work, or fails again down the road...STOP.

The more you screw with it, the more work it is to fix it. Can't tell you how many time I had to weld stuff like that up, machine it flat and drill and helicoil a new hole.

The more you work on it and jack it , the more I charged to fix it.

Like I said, at this point, as long as it is staying tight, leave it alone. If it has issues again, pull the head and have it fixed by someone with a mill or even a seat and guide machine. And they'll probably need an EDM and TIG welder if you're not careful.