<VV> repairing broken exhaust flange studs?

Frank DuVal corvairduval at cox.net
Mon Jul 12 01:37:17 EDT 2010

I am going to assume the ears are OK, maybe a little thin..., and just 
the four studs are broken.

I have tried most methods over the years trying to find the shortcut.

But the overall quickest is still, and you started right here, remove 
the manifold from the car.

Tools needed: a good bench vise. Cutting tool to cut stud. 1/8 and 5/16" 
drill bits. Something to power the drill bits ( I say drill, others say 
drill motor, now most say cordless drill). 3/8-16 starting tap and tap 
wrench. Lubes of various sorts, used motor oil if nothing else is there.

1. Cut the remainder of the stud off with a hacksaw, die grinder, whatever.

2. Center punch the shiny stud. It is now shiny since you cut it off. If 
it is already broken short, try to center punch the rusty spot. ggg

3. Drill a through hole with a 1/8" or so bit. Use lots of lube of your 
choice. Keep the drill as straight as possible.

4. Drill a 5/16" hole through the 1/8" hole. Again, use lots of lube. 
This is also where I practiced how to sharpen drill bits. It is amazing 
how short you can make a 5/16" jobber bit by breaking it and 
resharpening it! gggg

5. Tap the 5/16" hole with a 3/8-16 tap. A starting tap works fine here, 
as the tap can go all the way through. Use tap lube of your choice.

6. Install a stainless steel stud. I also use Never Seize when screwing 
the stud in.

7. If you use the brass nuts, DO use lock washers and don't use Never 
Seize. You will be forever tightening the nuts. I now use Never Seize, 
lock washers and regular steel nuts.

I have tried heat from propane, Mapp, and Oxyacteleyne. It never seems 
to loosen the stud to make it removable, and quenching it makes it so 
hard drilling is difficult when you resort to the above method.

Soaking them for days, well, days later I'm still doing the above procedure.

Sometimes you will have a surprise. The stud will start to loosen when 
drilling. If real lucky, it will screw out and you can skip the tap 
step. This never happens often enough on the east coast to recommend 
starting with left handed drills. Use the cheap regular drills. 
Typically you will not have perfectly centered the first drill bit, so 
the remainder of the stud will move during the taping stage, if at all. 
This can break a tap, just go slow and watch. If it happens, remove the 
tap and chisel out the remainder of the stud. You may need to make a 
chisel out of a round punch to get a small size. A good use for broken 
punches. You can still tap the hole. They seem to work well even if 
slightly oversize. Trust me...

Frank DuVal

Waiting for others to list their easier method! ggg

Ray R. (aka Grymm) wrote:

>Hello all,
>     All four flange studs are broken on the pair of exhaust logs I have for the 63'... any advice on the best way to do the job?..... particulars on tools would be great!  I already removed the manifolds from the car to make the job easier...   last time I did this (on the 65') I did it on the car... the result was tons of time spent, a sloppy job, and a back sore enough to send me to the emergency room!
>Ray "Grymm" Rodriguez III
>Lake Ariel, PA
>CORSA member

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