Exhaust Stud removal.. help please

[jriera]

Hi all, changing my heat exchangers to SSI's two of the studs decided to break, all other 10 came out fine. They have broken about 1/2 inch from the cylinder, I have tried soaking with PB Blaster (multiple times, 15 or so, over a period of two days) and nothing, they don't move, no threads left for trying the double-nut option.. So I guess is time for the MAPP-Oxygen solution..

After searching the board I have find out two conflicting answers on the proper way of removing the studs, one is heating the case and the other is heating the stud to cherry-red.. Which one is the 'preferred' one. The engine still in the car.

Also what additional precautions should I take while working around all the oil lines and such (aside from having a fire extinguisher and a hose close by)?

Thanks

Jordi Riera
73.5 911T
Richardson, TX

[rcwaldo]

I would heat the surrounding casting of the cylinder head. My theory would be to expand the aluminum around the stud. Heating the casting will in turn heat the stud as well. Aluminum expands more than steel so you will be ok.

Two of the twelve broke on my 74 while removing the exhaust. I was in a different boat though, the engine was coming down and apart.

I know this a VERY frustrating situation. I wish you success!

Chris

[beepbeep]

No problem!

Heat a nut and MIG-weld it on the stud, then heat head slightly and just turn then nut with a wrench...it will came of...in worst case you'll need another nut.

[pwd72s]

Originally posted by beepbeep
No problem!

Heat a nut and MIG-weld it on the stud, then heat head slightly and just turn then nut with a wrench...it will came of...in worst case you'll need another nut.

I vote for this method. Worked on my car, after I called a friend who happened to be a SAAB wrench at the time. Man,. am I glad Tim was around! But the "how stupid can you be?" look he gave me...after performing what he considered to be a simple chore? Oh well...live and learn.

[cary]

I second, Paul and beepbeep.
Mine was the same way.

Weld on the nut. Heat the head with the MAPP gas torch.
Give it a little crank tighter. Then back it out. Easy Deal .

Did mine in a 20 degree garage. So it didn't take much heat to break it lose, once to nut was on it.

Good Luck

[Jim Sims]

Good advice but I've also seen it go this way too: Pre-heat a nut and weld it on. Heat nut and stud cherry red. Tighten slightly and then loosen. Stud snaps off slightly below surface. Head comes off and goes to a machine shop for mechanical machining or EDM removal of stud remanents and installation of timecerts as required. Hope it goes well for you. Jim

[cary]

Jordi, Jim's right ..........
What worked for Paul and I, doesn't always work.

I also used PB Blaster. Great Stuff. Use the longest handled wrench you can. And GO SLOW.

GOOD LUCK ...........

[beepbeep]

Preheat the nut just to get best strentgh in your MIG-weld...

Do not heat the stud/nut assy, it will just weaken it...just heat the "hole" slightly so it widens...

[jriera]

Thanks for all the answers... unfortunately I do not own a MIG (I know.. I know.. about time to buy one).. so looks like the answer is to heat the aluminum case, vice-grip the stud ... and pray for a quick/smooth result...

Regarding safety.. how safe is to heat the case with all the oil lines around? any advice?

Jordi Riera
73.5 911T
Richardson, TX

[beepbeep]

Do not heat the case too much ... just enough so it thermally expands a bit...

As for MIG welding the nut...it might work with ordinary welder as well...i doubt vice-grip will hold....

[Jim Sims]

Safety:

Have an oil/gas rated fire extinguisher at hand.
Have a second person as a fire watch; this person will watch your flame and let you know if you're heating something you shouldn't be and will look out for fires. Clean off all the oil and grease in the vicinity of your work area. Wear eye and hand protection (fire watch person too). Have a pail of cold water available to immediately immerse you skin into if you burn it; if you do this right away it will minimize the damage. One can buy high temperature fabric flame and spark protection pieces to drape over items near the application of heat. One can often find these fabric pieces in the plumbing or welding supply section of stores. jIM

[cary]

More .02c.

I used my Arc welder on my nut. Couldn't get a good enough ground with my wire feed.
But heeding Jim and beepbeeps instructions you don't want TOOO much heat on the case. Just enough to get it done.

[cstreit]

If you don't have a MIG welder (I don't) here is what I did.

1. Get yourself a stud removal tool. It looks like a socket with cams inside.
2. Heat the case gently, PLEASE don't overdo it.
3. Tighten the stud SLIGHTLY,
4. Try and back out... don't overtwist, don't break., shouldn't take that much to get it out.

If this fails, since you haven't broken it below the case (right?) bolt on the pipes as best you can, and take it to a shop to weld on the nut and extract it.

[john walker's workshop]

then when it breaks off, file or grind it flush with the head, carefully centerpunch it, and drill a small pilot hole all the way through it. this is your only chance to get the hole in the center of the stud, so be careful. then use the drill bit in your timesert kit (you do have one?) and complete the drilling. do the timesert procedure. 1 out of 20 may come out without breaking regardless of the technique.

[cstreit]

LOL JWW... We at least PRETEND to be optimistic.. It does work sometimes....

[jriera]

Thanks for all the answers to this topic.. you have managed to scare the heck out of me so I will be tow/drive the car to my usual Porsche shop for them to do the work.. sound like fun to do but probably I'm just too 'chicken' to try it (fire, breaking, EDM, drilling...).

Thanks again for all the replies.

regards

Jordi Riera
73.5 911T
Richardson, TX

[Jim Sims]

Jordi, Sorry we scared you but I just wanted you to know what might happen. I have pretty much concluded there is always a chance of exhaust stud damage anytime heater boxes that have been on any significant length of time have to come off. Probably your mechanic will take many of the same measures suggested here but he is likely better equipped than yourself. We all have our comfort level and we respect that. I hope your mechanic gets all the broken studs out without resorting to machining! Good luck and let us know how it goes. Cheers, Jim

[john walker's workshop]

the proper way is to use an oxy/acet torch and heat each nut red before attempting to move them. deal with one at a time. you rarely break one this way. not everyone has a torch at home though. the propane type just aren't hot enough.

[Jim Sims]

When an oxygen/acetylene torch is not available I've heated parts using a MAPP (Methylacetylene-Propadiene) gas torch burning in air. It's a lot cheaper (one can get them the size of a small hand held propane torch) and in many ways safer than an oxygen/acetylene rig. Bottles are disposable like propane. In air, MAPP gas burns at about 3650 deg. F as compared to 1400 deg. F for a propane torch burning in air. For reference an oxygen/acetelyene torch produces around 5875 deg. F and carbon steel melts around 2700 to 2800 deg. F. Jim

[cary]

I was going to spout up with the same comment as Jim's.

I have one of those Portable Torches from Sears. Uses a small Oxygen bottle and a MAPP disposable bottle. Not a heavy duty rig. But works for the stuff I'm capable of.

When I removed my heat exchangers. Tried the plain MAPP torch in a 20 degree garage. Barely changed the color of the first nut. But it came off. Wasn't till I broke the second one did I remember I had the torch. In 15 seconds the nut was cherry red. All the rest came off just fine.

I have NO luck, so I must have done something right ...........LOL..

I think what John's trying to tell us, for the umpteenth time? If you haven't had exhaust hardware off if some time. Quickly expand the nuts. By heating them cherry red before you attempt to remove them. Rather than having to repair the aftermath.