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?