Exhaust stud broken - now what?

[Clark Griswald]

Got a good deal on a set of early heat exchangers. So decided to backdate the 77 exhaust system.

I was apprehensive about loosening the exhaust bolts, given they have some 240k miles on them. Gave them a good dousing of liquid wrench. To my surprise they almost all came out easily. Some of them came out with the stud, no big deal.

But one was stuck. Tried heating it. Seemed like that broke it loose, but it kept getting stuck as I loosened. Then it snapped.



Seems some of the studs rusted in the center, weakening them.

Although the shadows make it hard to see, this following picture shows two studs that are thin in the center, presumably due to rust. The one on the right is the same thickness over the entire length.



I will replace the rusted studs.

I am looking for recommendations on how to get the broken one out of the head. As you can see, a good size portion of the stud is sticking up. So I can grab it with vise grips or similar.

However the diameter of portion I can grab is small due to the rust, the amount of torque I can apply will be limited. And it is in tight enough that it snapped in the first place.

When that doesn't work and the rest of the stud snaps off, I am thinking a screw extractor. Has anyone had success pulling a broken exhaust stud this way?


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Chuck Moreland '86 Cab - "Sparky", '77 Targa - "Sweet Pea"

[This message has been edited by Clark Griswald (edited 10-16-2001).]

[Kurt B]

No answer, but thanks for the pics! I've never seen those things up close before, or a broken exhaust stud like that. need to archive this thread.

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1984 Rockin' Cab
www.geocities.com/carrera_cabriolet

[ovilla]

Had the same problem with my 75 914. I was doing a valve adjustment a week before the Tweeks show and had decided to drop the SSI heat exchangers for easier access. Anyway, I didn't have any threads left on the broken stud and couldn't take time off so I took it to my Porsche mechanic. He welded a nut on to the stud and then heated up the stud at the base. I forget how hot he had to get the thing (he mentioned that it turned an orange-red color) and that's when the block released the stud. I then had him replace all of the studs on that side of the block since they were all originals and they always came completely out of the block anyway. Good luck.

[Bruce Johnston]

A good tool shop should have a tool that looks like a socket but it has teeth in it to grip the stud. You tap it on with a hammer then put your socket wrench on the socket and turn it out. Take a old stud to get the proper fit.

[speeder]

You may want to try a product called "Blaster", comes in a spraycan and disolves rust like nothing else. It will penetrate even in upwards direction, I buy it at Pep Boys here in CA. My machine shop guy turned me on to it, swears by it, it is specifically for your situation. Give it a couple of treatments and let it soak, then try to turn rusty stud gently,(so as not to break it), maybe use heat as well. If this works it will save you a big PITA. Then just replace ALL the studs and you're back in business!

[beepbeep]

Been there done that!

I had plenty of broken studs, stripped threads and missing nuts on my 930. It has alu heads, dunno about yours.

Cure:

* Buy new pins and nuts, *all* of them.
* Buy new gaskets
* Take out all old pins from the head, exhaust shops have nice tool to take them out. Use heat on those that are stuck (use torch,it takes more than a cigarette-lighter)
* Extract those that are stuck with "pigtail" (do not try to drill it out, you'll just screw the holes)

Now you can take two paths:

Prefered:
* Drill all holes to 10mm oversize
* Insert helicoils in each one of them
* Insert new pins, use new gaskets, assemble exchangers and tighten to 25Nm with torque wrench.
* Drive it around for decades

El-cheapo:
* Use thread-cleaner on each hole.
* Insert pins
* Assemble exhangera , try to tighten it with 25Nm, watch few pins just turn around in threads, drive and wait for leak.

Cheers!

[derkpitt]

If your sure it will brake off, try using a drill bushing to drill a small hole right down the center. The first bushing goes tightly around the outside of the stud.
the next will slide down the center of the first. Giving you the center of that stud, before you brake it off flush. The drill bushings come in all size, to get you down too the smallest size to drill.
Make any sense?

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Derk Pitt
88 Carrera Coupe

[jabb]

I would use the PB Blaster to start with to soak for a couple of days. Heat is the way to go... Weat cycle the stud 3 or 4 times...
you have to get it glowing red. After it heat cycles heat up one more time put a ViceGrip on it and give it a try. Luberciate it as it starts to come out.

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• Joe A.
• 84 911 Targa
• 75 914/6 3.0

[john walker's workshop]

those studs with the narrow shank are original units, used with the original thermal reactors. if you twist it, it will break off. most of them do, heated or cold. (think about it, a softened, red hot stud will simply twist easily until it breaks). when it does, file or grind it flush with the head surface, carefully center punch it, drill a small pilot hole dead center, then use the drill size necessary to tap for a timesert, or a helicoil at last resort. the dead center punch mark and dead center pilot hole are the most important steps in a successful repair.

[GIBSON]

If they break off above the head you'll be ok. They can be ground flush and it's easier to get a dead-center punch. The problems I've had are when they break off at an angle down in the head. That creates a harder job.
Is there a way to deal with that?
Also, I've had some luck with reverse drill bits, backing the broken stud out as the drill size goes up.
Bruce Herrmann

Bruce Herrmann

[Superman]

Spray penetrant on it several times over several days. it sounded like you might have felt that it started backing out, then got stuck and broke. Whether or not this heppened, you should try to turn it clockwise first. If it turns clockwise a little, you are in good shape unless you get impatient. Using penetrant, and taking days if necessary, turn it back and forth until it comes out. Heat is a great tool, but I imagine John is right...those thin shafts probably will just twist if heated.

Drilling, if that is necessary, should be done with maximum precision and patience. Unfortunately, the stud is probably twice as hard as the head it sits in. VERY easy to damage the head. VERY.

Once out, chase the threads to clean them, and use the fancy copper heat-resistant anti-seize stuff. Use the highest quality, all-new studs you can find. Some folks like stainless. I'm on the fence about stainless fasteners in high-heat applications. Sometimes they work very poorly.

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'83 SC

[Jdub]

What concerns me is that the stud became harder to turn as you turned it out. Spiral of old alum. thread gumming things up in there? Possible stripped threading now?

The oversize drill/helicoil seems the ticket to me.

Jw

[Clark Griswald]

Tried heating it again, then twisting with vise grips. No dice.

Those vice grips just don't hold that thin stud tight enough. It is about 3/16 inch diameter.

So I bought a special stud extracting socket. This one has a toothed cam that squeezes the stud. Unfortunately it wouldn't clamp down. It is really designed for 1/4 inch and larger.

I am going to try and find a similar tool designed for smaller studs.

Upon further inspection I see that at least one of the studs had been previously helicoiled. I am guessing the one that snapped is not helicoiled since it is one of the original thin studs.

Superman, it did FEEL like it was turning. But that may have been the metal fatigue. Or it may have been the actual nut turning on the stud, then getting stuck and snapping.

I hate to drill this thing. I would have to cut it off flush at the head first, and I don't have a good way to do that. I would probably need to buy a dremel tool with a cutoff blade.

[Early_S_Man]

Before you mess up the head, you may want to check around for a shop that has one of those EDM-machines on a lift/jack that Wayne mentioned a while back in one of his excerpts out of the new book.

And, you don't want to put in a Heli-coil ... make sure it is a Time-Sert or the oversized Big-Sert for an 8 mm stud!!! Check their info ... here:

http://www.timesert.com/bigsert.htm
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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[This message has been edited by Early_S_Man (edited 10-17-2001).]

[Todd Steele]

I experienced John Walkers scenario exactly. Did the heat, the solvent, stud pullers wouldn't fit, ended up breaking two off and drilling them out one bit size at a time.

Follow S-mans advice on the inserts I used his advice and it gave me the cleanest repair. Used Heli-coils many times on my bikes...after using Timeserts I'll never use a Heli-coil again.

FWIW,Todd

[Roland Kunz]

Hello

One trick is to loose the nut by removing all rust on the threads and then slightly working down and up again to get the rust out of the thread.

Grüsse

[cary]

Just thought I'd add my .O2.

I followed Bruce Anderson's broken exhaust stud instructions in the Performance Handbook. To the letter.

Worked exactly as described.

The product everyone was talking about, is called PB Blaster. Awesome product.

Good Luck

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Cary Kutter
77 Euro Carrera w/3.2
74 914 2.0 ( base model )
PCA Region - Big Sky

[This message has been edited by cary (edited 10-19-2001).]

[Clark Griswald]

Got the job done. It was a pain in the ass.

As I continued with this project, I realized the early style exchangers have thin flanges, the new style have thick flanges. Hence the studs are designed for thick flanges and have a lengthy non-threaded section.

So the plan was to remove ALL studs and replace with the shorter factory studs. Some came out, some didn't.

I used plenty of liquid wrench, and torched them several times. They just didn't budge. I think they were installed with the red loctite.

I bought two different types of stud removing sockets. Neither did the trick. They just couldn't torque the studs enough, one more did break off however.

Long story short, I ended up cutting off, drilling out, and heli-coiling 4 studs. It worked okay, but I wish I had followed the recomendations for using time certs instead. They are better, but I couldn't find any locally.

The worst part was cutting off the studs. I used a Dremel cut-off wheel. They cut clean, but take forever. And they are brittle and break. Good thing they come 36 to a pack. I used about 40.

All said and done I had spent about $150 on tools and hardware. Turning my bargain $150 exhangers into a $300 ordeal. Still a pretty good price. Had I popped for new SSIs, I still would have had the same stud problems.

And the performance........

Outstanding. The car is noticably more powerful. Probably would stomp a stock SC.

This really is a great update (backdate?) for CIS cars.

With the new exhaust and the recent suspension changes I've made, this '77 is really starting to kick ass.