[ktemkin]

Cheapy catalytic converter, installed by previous owner, died.

Pulled old cat and discovered that bracket holding bottom of exhaust manifold to block was broken and the head of one of the two bolts at the manifold was rounded-off by someone's previous repair attempt (because of obstructions, a socket and extension does not seat flat on that bolt head and I suspect a previous attempt to remove the bolt with an impact gun destroyed the bolt head).

Removed bracket.

I wire brushed the whole area and for three or four days sprayed the area with PB-Blaster several times each day.

Decided to cut a slot in the remaining head of the bolt.

Heated the manifold casting w/oxy-acetelyne and, using a straight bit from an impact driver with a 1/2" impact gun at 40psi, attempted to break the bolt free.

Ended up breaking the straight bit. BTW, used 40psi because I didn't want to break the bit, my goal was simply to repeatedly shock the fastener so that, ultimately, it would free up. I've been successful previously with many rotted fasteners using this method.

I've kind-of used up my standard bag of tricks. At this point I believe I have three options:
1) remove the manifold by separating it from the head and deal with the rotted bolt in a much more comfortable arrangement.
2) weld a nut on the remaining head of the bolt and continue to try and impact drive the bolt out.
3) accept defeat with only one attachment point supporting the bottom of the manifold.

I started option 1) and, with a 1/2"-drive, 18" breaker bar, attempted to loosen any of the five manifold-to-head nuts/bolts. At the point the breaker bar was bending a good 10-degrees without breaking free the fasteners, I decided the last thing I needed was to snap off one of these nuts/bolts. I abandoned option 1), although I am considering bying a cheap, Harbor Freight right-angle impact gun to free those fasteners.

I have prep'd for 2). Plan to lightly MIG-tack a 1/2" nut to the washer (to hold the nut in place). Then remove the C-clamp and weld the inside of the nut to the rounded head of the bolt. Then file away that external tack and try impacting the bolt out.

Option 3) is always a possibility.

Any suggestions?

 

[Mcdirtymetal]

In the past, I have knocked the head off the bolt with a grinder or cut off wheel and drilled a hole and tapped it.

 

[ktemkin]

Because of obstructions, while the manifold is still in-place I won't be able to drill a straight hole through the existing bolt. If I decide to, and if I am able to remove the manifold, I will be doing what you suggest.

 

[DCM]

Removing the whole thing really makes it a lot easier and less frustrating to work on, although wiggling it out is a test of patience

 

[ktemkin]

Removing the whole thing really makes it a lot easier and less frustrating to work on, although wiggling it out is a test of patience

Yes.

I am just concerned about breaking off one of the five (I think five) nuts and/or screws holding the manifold to the head.

If I break off one of the fasteners, that brings the repair to a whole new level. Nothing I can't handle, just a whole lot of headache and time.

I think I read in one of the threads that breaking one of those fasteners happened to someone and they drilled out the fastener while the head was still on the block. To be honest, I don't see how that would ever be possible, unless you are using a dental drill !!!

Thanks. Ken

 

[DCM]

Realistically, I don’t see that running with one broken bracket bolt will cause you any issues.

 

[ktemkin]

SUCCESS !!!

Welded a 1/2"-13 nut onto the remains of the head of that bolt.

Whole area was red hot from 30 seconds of continuous welding.

Pulled out the air impact and it backed right out.

Nothing like heat and a good grip to free a seized fastener.

Thanks all for all the suggestions, some of which I would have to turned to if the welding project was not successful.

 

[DCM]

Nice work! Now run a tap through the nut, and assemble using nickel anti-seize