Broken exhaust manifold to converter studs, two on each side, are giving me fits.

I tried heating (with a mapp gas torch) and visegrips. Got it red. Wouldn't budge. All I got for my trouble was a hot metal splinter in the eye.

Tried drilling with cobalt bit. Access is difficult, and the bit didn't seem to be cutting at all. I will try again with a different type of bit.

My first idea was to remove the exhaust manifolds. Started with the air tube nut. Wouldn't budge, and started deforming the nut.

No amount of penetrating oil and time does any good.

Other than another go at drilling, I'm out of ideas. Open to suggestions.

 

I've used nut splitters on stubborn exhaust nuts. Not sure if it accessable or applicable.

 

My wife's Blazer converter broke up inside and I had your difficulty getting the nuts off. Eventually bought an air driven mini-die grinder with a thin cut-off wheel and cut the studs off just under the nuts. Tight fit but the mini size was just small enough.
Couldn't get the cut off studs out of the manifold flange so cut slots into the flange (two cuts each slot) to the sides of the studs. Studs fell out. Used 'normal' bolts for the reassembly. The slots were cut edgewise to the studs so the assembly was supported with the bolts in place. In other words, two slots were horizontal, one was vertical.
Hope you get the picture and good luck with a tough job.

 

If you want to try penetrating oil again, try Kroil. Look it up at KANO labs. Best I've ever seen.

I'd go to Menards and buy a MAP & Oxygen torch for under $50. Heat the manifold - not the stud -till it's cherry. Use a stud extractor (goes around the stud and grabs it when you turn the wrench). And please wear glasses

Good luck!

 

Yeah - you need a "real" torch, something that is fuel/oxy. Then you can either heat the manifold flange enough to do some good, or just burn out the studs.

Then re-tap the holes. Then use Stainless steel studs with Brass nuts on re-assembly - Next time will be Easy...

If you can't find stainless studs you can get them at Danchuk (Tri-5 restoration parts and other neat stuff you didn't know you needed).

Any auto parts place ought to have the brass nuts, or even the hardware store..

 

Okay, picked up an oxy/mapp at Lowes. Fifty bucks. With it I was able to get the flange a reasonable shade of red. Still no budge. Nice little torch though, I'll find uses for it.
Giving up on spinning the broken piece out I decided to cut the stub off and grind it flat. It did not cut easily. With a flat surface I was able to start drilling pretty close to center, although with the drill in position my view of the work was completely blocked. The cobalt bits seemed to become dull quickly. It took me four bits to get all the way through.

Step One

From this point the drilling went easily. The hole was slightly off center. I tried to collapse the shell that was left on the long side but ended up having to drill all the way to 11/32.

Step Two

After chasing the threads, the stud went in securely enough. Not perfect but good enough. Some red loctite and it isn't going anywhere.

Step Three

One down, three to go. The last one on this side is right under the motor mount bracket. The bracket will have to come off for access. Debating on whether that should be done now or after the transmission is back in place. This view makes the studs appear crooked but they really aren't.

Alternate View

Elapsed time, about four hours, including time spent torching and a couple of trips to pick up additional tools.