Cylinder stud replacement

[richclare]

Hi,

I had a problem with a cylinder head stud not tightening, which then led to a water leak. I stripped the top end, thinking the thread or bolt had stripped, but it seemed OK. I then removed the old stud and found it had been bent to realign an otherwise wonky crankcase threaded hole! I believe it was the stud that was pulling from the crankcase, as the thread didn't look good. The attached photos (sorry about bigfoot😉) show the new 'straight' stud and how far it is out.
I was going to set up a level jig on a pillar drill, redrill the hole, straight, and fit a helicoil. Would this be a good fix in people's experience? I have never used one and would appreciate any advice relating to the repair.
Also I'm not sure how the threaded hole ended up 'wonky' as the thread size is original😨

Many thanks,

Rich

[Tobyjugs]

Check to make sure the hole is not heli-coiled, it seems strange that it is not straight.

If you have enough room a heli-coil will be fine.

I think the biggest problem will be trying to re-correct the angle of the hole as a standard drill bit will try to follow the old hole.

[coose]

If it has already been helicoiled you could fit a timesert as they generally have a larger OD.
You could drill it with an end mill as they have four flutes instead of the normal two of a drill or a slot drill, so there's less chance of the drill wandering. An end mill isn't technically designed for drilling a blind hole, but in this case you're boring an existing hole so it should be ok.

[richclare]

Thanks tobyjugs and coose. I appreciate your thoughts. I thought if I took it very slowly, it would help the wandering, but the end mill is a nice idea - just need to find one!
I took another photo of the hole, but close up.
Thanks again for your time.

Rich