Header stud drilled entirely off centre, options? (or: retarded PO strikes again)

[SkiMachine]

Here's the PO's solution to a broken exhaust stud on the passenger side:

Stove bolts are high-strength rated, right?

 

I saw this when I purchased the truck but at the time everything else looked good. In hindsight this should have been a monumental red flag and I have paid the price dearly since. At the time I thought it would be a straight forward drill out and replacement with the correct stud, until I saw this:

Not on centre at all. And it appears that he was drilling even further away from centre (and into the head) the further in he went:

. (this is a new, straight stove bolt) Good thing he only drilled about half the length of the original threads.

 

So basically it looks like the existing threads are probably done for, which will mean there is no backing this stud out. I'm assuming I can drill out an extra size up to get a heli-coil in without hitting a water jacket, but what I'm struggling with is how to get back on centre to do so?

 

Any ideas?

[SkiMachine]

Uhhh, Tapatalk kept telling me this post was not submitted since I was posting too fast (even though I had not posted anything recently). Apparently this was not the case. Can a mod please delete all the other threads and merge any replies in those threads into this one? Thanks.

[SkiBumBrian]

Soak that puppy a few times over a few days Liquid Wrench, PB Blaster, etc) and try a left handed bit slightly larger than the one he used. Might back out. You could still try an easy out with it off center that much but the only drawback is they are brittle. You break one off in there and you are ****ed. Not as bad as it might seem. If you are REAL worried about it being off center you could build a jig using the other bolts with a sleeve and drill your own hole more centered but I think you can get it out just the way it is.

 

Good Luck! ( maybe Mr. Machinist will chime in with some expert options...)

[5523Pathfinder]

For studs that are drilled off center like that, what I have done is take a larger bit, a bit larger than the stud, and drill the "face" of the stud and hole. Yes, this does remove just a small bit if head material, but will recenter for a smaller drill bit. Use a small bit and remover and walk it out. I have also used a automatic center punch to walk the stud around and out.

[adamzan]

This is what I found in mine....Outside of it looked like a bolt, so I thought no big deal. Yea, what a **** that was.

 

[Precise1]

 

Ok, so what you are saying is that there is a stud still threaded into the head but broken off roughly flush, and the PO drilled off center and off axis to the center of the stud, and then tapped that crooked hole? I'm assuming the tapped hole breaks out of the side of the stud and into the head material? It also looks like the very edge of the hole is tangent to the center of the stud, which makes things more challenging...

I'm not sure what equipment you have available, but I am assuming you are more concerned about the best results rather than the fastest so..., I recommend a combination of Mr Bum's and Derek's recommendations, but starting with the least invasive or damaging first.

Soak the hole with a good penetrant, the hole will actually allow really good access for the oil so it could really make a difference.

The tapped hole could have also relieved the pressure of the frozen/broken stud and it might not really be very tight anymore. Can you get anything to the hole sideways (like a broken drill bit, ejeector rod, etc) so you can see of you can tap the stud counter clockwisevia the offset hole? In the picture, towards 1 o'clock would be the best, but try not to damage or displace any material, just see if you can get it to move at all.

The next step would be to drill it out and using a jig would be perfect, but it would take some careful measurements/fab work to do it. I'll try to think of the easiest way to make one accurately if you are up for it. If you can get in there with a dremel, some patience and a steady hand, you could start going down the center line of the stud with a christmas tree or V shaped burr until you have a partial lip all they way around allowing you to start a small drill directly down the center (measure the other holes so you have a maximum depth to shoot for and use a drill stop collar). Obviously, the first hole is the most critical one so take your time. Once you have a hole all the way through, try tapping the stud CCW again. If no movement, go to a slightly larger drill, rinse and repeat.

Any material you remove is a good thing, relieves pressure and makes it more likely to get the stud loose and out. Obviously, use left hand drill if possible and be patient.

I'm a little leery of Dereks large drill bit method, just because I don't think it would be possible to get it started properly, but I've not tried that myself by hand.

 

What kind of equipment do you have access to? Do you know anyone with a mill? Can you get a better picture like #2, but with the gasket pulled aside and the surface brushed or blown off?

 

Oh, I have heard of people tack welding a short bolt to the end of the stud as well, and using that to try to unscrew it, but if you do, make sure not to fill that hole or its never going to unscrew!

 

B