Broken head stud removal without engine disassembly - insanity?
 

Ok, many of you will think I'm crazy for even suggesting this, but it has been a long cold winter, so perhaps insanity has finally set in :eek:

We have all heard of, or experienced, the broken lower head stud(s) dilemma.

I'm wondering about, and willing to fund the associated R&D for, designing a tool that could extract broken head studs without disassembling the engine.

A fellow Pelican sent me a PM about this a few months back. Apparently he used a solid steel rod with a diameter just a little smaller than the head stud channels holes in the 911 cylinders, with one end machined to grip broken head studs (assuming, of course, that the studs are not broken flush).

Sounds highly improbable, but I'm thinking that such a tool would be invaluable :)

Crazy idea?

To start - does anyone know (or can they please measure) the precise diameter of the head stud channel holes, and the diameter of head studs?

I just replaced mine on my 3.2. I had a hard time with engine out and cylinders off. 27 years and red lock-tite is a tough adversary. Actually to begin with I did replace 1 without totally disassembly. I had engine out for clutch replacement, while out and adjusting valves I found 1 broken. I removed rocker/cam box and the 1 head of the broken stud (#4), I slipped the cylinder up and was able to get vise grips and heat on the stud, you have to be very careful with base gasket. After replaceing the stud, I think it was the next day and heard the "PING", you guessed it, while sitting on the ground another one broke. I ended up removing cylinders and replacing all studs with SUPERTEC, no regrets. If I had a "special tool" I definitely would have tried it.

Excellent, thanks for sharing. Yes, red lock-tite is indeed tough, heat is a must!

there was a post a few years ago where a guy accessed the stud where you can see it between cylinder and case and actually managed to turn it 1/100th of a turn at a time and finally got it out. probably took a fair amount of time, beer, luck and patience. no way i'd do it.

That sounds cool too. I'm assuming he applied heat?

some come out fairly easily without heat and some need a ton of heat. he obviously had one that could be accessed, rather than a front or rear one. see if you can find the thread with a search. been 2 or 3 years at least.

You could make a tool for the job but it's not as simple as removing the broken one and replacing with new.
What about the cylinder to head seal? Once a stud is broken this area often becomes coated with soot and oil and even if you put a new stud in... Would the head and cylinder seal properly?

If I ever found one it would be engine out and disassemble etc... I learnt a long time ago it's best not to cut corners with a 911.
They're great cars but you have to do it right the first time or else you'll be doing right eventually anyway.

Thanks, yes, wise advice to consider.

I would never turn it 1/100 inch at a time. I disassemble the engine first

I wonder what % break off flush, I thought it was most of them?

If one is broken they're all going to break.

Agree, if you have one broken one, you really should do them all... I also echo that cutting corners with these cars usually does not end well. My main concern aside from the longevity of the neighbour stud I did not change, would be the cylinder sealing.

There's a lot of good reasons listed above not to do this.

Another observation from my recent rebuild: I don't think there's enough clearance in the cylinder holes for a tool. I haven't measured it, but I don't think there was more than about 0.040" radial clearance from the edge of the hole to the edge of the stud.

Thanks - here is a quote from a Pelican friend that send me some details of his custom tool:

"I'm not positive on the exact sizes but the tool is easy to make and worked perfect the first time I used it and probably wouldn't be reusable. I took a solid piece of 3/8" (0.375") cold roll and drilled about a 0.300" hole in the end of it to press over the 0.305" O.D. head stud. I chamfered the hole so it would start easier onto the head stud. The idea is to have just enough press fit so you can unsrew the head stud. I carefully tapped the tool over the stud and twisted the head stud out. I really was impressed that it worked that easy".

I am thinking of making the above tool, with some improvements ;) to enhance grip to the broken stud.

I fully appreciate that Plan A is to remove and disassemble the engine + replace ALL lower studs, but some folks might still be interested in using the special tool.

Many thanks, but the commercial tool is for exhaust studs, not head studs.

Any additional comments or suggestions re above?

Special tools........
 

Newfie,

This special tool would only work if you have a loose head stud/s. Most of the time, they are stubborn and difficult to remove with the engine intact. This special may have been successful getting off a few of these dilavars head studs but I doubt it could be used as dependable or reliable stud extractor. I have a friend who had a single head stud broke at VIR and was replaced by a local mechanic. And the car was driven back to Pennsylvania. But this was a rare case where a broken head stud was already loose and easy to replace.

Once the Dilavar head stud/s start to fail, the next prudent course of action is to replace all these 'ticking time bombs' with steel head studs.

Tony

In my case I used heat (MAPP/OXY torch) to help remove all the studs. I do not believe that the described tool would have worked in my case without the heat... With the heat, it may have been possible. I still had to apply a fair amount of torque even with the heat (although much less than without) and it is hard to say whether the press-fit tool you are describing would have been enough IN MY CASE. However, some people have had studs that seem to have turned with considerably more ease. You won't know until you try. But I still maintain that if you don't replace the other studs, you are likely on borrowed time, and I would also want to replace a cylinder base gasket...

Thanks - For the press-fit tool, I am thinking of machining the id to provide a better grip to the broken stud - any suggestions?

It should be possible to apply heat to the broken stud area with the engine still in the car, correct?

I agree, Plan A should always be to remove the engine, disassemble the engine, and replace ALL lower studs + gaskets, but the Plan B tool might help some get out of a jam, especially if the broken stud is discovered shortly after it breaks (before additional damage occurs), which would, of course, require regular inspection of all the lower studs.

I recall he said it took him 8 hours to get one stud out, and gave up after that. how valuable is your time?

Being able to do it is one thing. How about what other potential issues are lurking in there that will go unattended to? I'm not trying to say that complete teardown is always a must. But sometimes you come across other things needing attention that are fortunate discoveries "while you're in there."

You may be "lucky" that the head studs are loose. That's how I recently found all of my head studs on my '79 engine. When they were last replaced, they were not threadlocked in place. They only had some nasty smelling gray paste on them. So they were easy to remove. I used two M10 nuts double-nutted on the studs and they all turned out with a mild amount of effort, using a std. 17mm box wrench.

Thanks - I think the 8 hours is referring to the guy that used vice grips to turn the broken stud very slowly.

In 8 hours the average person could remove the engine, separate the gearbox, and get the engine partially disassembled.

To start - does anyone know (or can they please measure) the precise diameter of the head stud channel holes, and the diameter of head studs?

I'll bite...
My 3.2 heads measure 10.5mm diameter at the smallest point. The four holes start out from the top at 24.5mm,dropping 50mm before reducing their size to the 10.5mm.The difference, of course, due to the diameter of the head securing washer and nut. The fourth hole, by the spark plug, provides a bit more access in the beginning, but at the 50mm mark also reduces to 10.5mm. The head studs are 9.84mm at the thread, and 7.64mm nominal for the shank. Good luck with your project.

Excellent info - thanks very much - I can't locate the broken head stud that fell out of my 3.0 engine, but I'm assuming that the dimensions will be the same.

So, the maximum O.D. of the tool will need to be slightly less than 10.5mm, with a tapered I.D. suitable to grip the 7.64mm shank.

I'm hoping to make a prototype removal tool soon ;)

Don't do it half assed, do it the proper way.

Well I guess I'll chime in here. I have been working on a tool to get these things out. Here it is and it is in the testing stage. It is made out of a craftsman extension and works a bit like that toy that you put on your fingers and then you cannot get your fingers out. You screw it on with a bit of pressure and then it really locks on. Looks to be promising.
http://forums.pelicanparts.com/uploa...1332014427.jpg

http://forums.pelicanparts.com/uploa...1332014472.jpg
http://forums.pelicanparts.com/uploa...1332014516.jpg

I think this is a great idea. Imagine being at an event and having one stud break (or you realize one has broken). You can just pack up and go home where you can remove the engine and do a top end rebuild while you are at it. Or you can haul out your trusty stud extractor and a spare stud, do the fix, and you are back in business. Then, when you get home again, you can ponder your next steps.

When I finally raced at Sebring it was a 4,000 mile round trip. I'd have hated to have a mechanical issue rain on my racing. I'd not have thought twice about taking the chance that there was some seal damage or that others would soon break. Speaking of which, I don't see that the copper base gasket would likely be an issue. The C shaped head seal, for cars which have that, could perhaps have gotten damaged. But guys have from time to time reported finding amazing numbers of broken studs and the motor still ran well enough, or so they thought.

So I'd say this would be a fine special circumstance tool. And a challenge to the tool maker. Cut channels for some carbide gripper pieces to be fixed in the ID so it will really grip but can be reused? Though maybe as a special purpose, just one broken stud, tool reuse might not be important.

Excellent! A Chinese-finger stud extractor! Not quite what I was thinking of, but maybe better!

Have you had much success with it yet? What is your plan with respect to application of heat to the broken stud area?

Thanks - very good points and suggestions to consider.

The intent is a one-time use, special circumstance tool, to be used when you become aware that a stud has broken, you don't have time for a full top-end tear-down, but you want to prevent additional damage.

The heat issue is the real killer. If it is a top stud then it's pull the motor time unless you have carbs then it might be worth pulling the fan shroud. On the bottom you can actually heat up the metal air defectors and bend them out of the way to get the heat pretty close to the stud area. Heat exchangers pulled off of course. The tool is really pretty cool, it grabs the stud very hard, almost to hard, I might have to shorten the spiral section. I hope to test it this week on a motor that is out already and see if it holds up.

Thanks :)

The bottom studs are the ones that break; I've never heard of a broken top stud.

The tool does look very cool - what type / size of material is the spiral section made with?

Looking forward to your update, and images ;)

I have been looking at the tool for a while and I believe it could grab the stud.
But doesn't almost the entire torque you apply concentrate to the top spiral? If so, I think it will snap like a straw...

Hi,

How about EDM (Electrical Discharge Machining)? Shouldnt be to hard to make an electrode. The hard part would be to make sure you only machine the stud, not the engine case.

Done right this should only leave parts of the stud threads in the case, which would be easy to remove with a thread tool.



Regards,

Johan

Another suggestion from above - assuming the stud is broken close to the case:

With the engine tin moved out of the way, it might be possible to use a two-piece tool; the lower stud gripper could be as large as the space allows, with a hex socket to engage the second piece - a simple long socket extension that is small enough to pass through the stud channel in the cylinder.

Thoughts?

What I have seen often, is when one or more stuts are broken the head gasket is broken,too.

The spiral section is just the craftsman extension machined down then drilled and then the spiral is cut into it.

This photo was to show how the tool worked. In actual application the spiral cut would be pushed all the way over the broken stud. It will push all the way over the stud but it is just very hard to remove the stud out of the tool so I only installed the stud part way in the photo. This tool still has to prove itself, hopefully it will work. If it breaks it is back to the drawing board.http://forums.pelicanparts.com/suppo...leys/smash.gif

If you need a ginny pig look no further. My lower stud on cylinder 4 broke. I don't know how long a stud is http://forums.pelicanparts.com/uploa...1332137896.jpg
but this is what broke off.

Yes, I assumed that you push the broken stud up above the spiral so that it is supported. I think you would have to make the spiral progressively wider toward the top to make it stronger.

But still, having replaced studs from 2 engines, I know how much force that is needed to make them come out.
There is also the possibility for the tool fail, brake off and jam up the cylinder on the stud. Maybe even cause damage to the cooling fins.

Hi - can't wait to hear the results of your testing - Best of luck :)

Hopefully it will have enough grip to lock onto the stud securely - if not, perhaps my now revised (and evolving) plan to use a solid steel rod with a tapered hollow end + carbide gripper pieces (as suggested by Walt - see above) might work better?

In either case - application of heat http://forums.pelicanparts.com/suppo...ys/flaming.gif is the key process!