Heli-Coil advice?

[Stelth]

I have a broken exhaust manifold stud that I'm trying to deal with. I tried a screw extractor, and as usual, it broke off in the stud. So now I'm trying to drill the stud out, in hopes of using a Heli-Coil to fix it.

I got a kit that says it's for M10 1.25, which is what the stud is, but the drill bit and the inserts look enormous compared to the M10 stud. M10 is about 1/4" diameter or so, and the kit recommends a 13/32" drill, which is a *heck* of a lot bigger. Is that OK?

 

[jkhawaii]

yes, you will need to drill the hole larger to install the heli-coil. I have been a automoive tech for over 15 years and I still hate broken bolts. one issue you may run in to is you may drill to far or off center and drill into the coolant jacket. its not a fun task. can you reach and see the broken stud easily?

 

[NHGUY]

6 is around 1/4",13 is around 1/2".So 10 is between the two.

 

[Stelth]

Originally Posted By: jkhawaii
yes, you will need to drill the hole larger to install the heli-coil. I have been a automoive tech for over 15 years and I still hate broken bolts. one issue you may run in to is you may drill to far or off center and drill into the coolant jacket. its not a fun task. can you reach and see the broken stud easily?


It's in kind of an awkward spot (v-6). I've fashioned a drilling guide out of a pipe nipple that I've inserted into the exhaust manifold to center the drill bit, so that hopefully I can center the hole. I've bolted the manifold in place. The drilling is going slowly, and I'm using a magnet to see if the shavings are aluminum or steel. Fortunately, I'm getting mostly steel at this point. As I'm typing this, I'm waiting for the glue (yellow weatherstrip adhesive) to set up where I've glued the pipe nipple into the manifold.

 

[beast3300]

Once you get the Heli coil in just remember to break the tang and remove. It will work.

 

[expat]

Is the stud broken almost flush with the head surface?

If so, I have had good luck drilling a small hole in a metal bar, then welding to the stud end through the hole.
The bar is then used as a wrench to remove the stud.
I guess the heat from welding also helps.

Oops, too late, I see you are already drilling.

 

[mechtech2]

The guide is a great idea. Those hard studs/bolts are TOUGH to drill on center.
I'd file/grind it flat first, if you can.
Torch heat will loosen it. Get it red hot and the bond of the metals will break.
I also hate broken exhaust bolts - the worst.

 

[Trav]

Quote:
I tried a screw extractor, and as usual, it broke off in the stud

This is going to make it much harder i think.