Jump to content

Broken studs


Leland Davis
 Share

Recommended Posts

I had a shop in the early eighties where we remanufactured VW and Porshe air cooled engines. One of the things that I had to constantly deal with was broken studs, primarily on the cylinder heads. People would strip down their old engine to the long block and exchange it for a freshly rebuilt one. Did about 3000 engines in a five year span. So often, the exhaust studs would be snapped off when removing the muffler or manifold. How does one replace a broken stud? After lots of practice, I became a wizard at it. 

    The worst thing that can be attempted is to drill the stud and try to remove it with an EZ-out. Invariably, the EZ-out would snap off in the hole, and then you are screwed.  What I would do is to drill a 1/8" hole directly down through the center of the stud. The trick is to get the hole exactly centered. Then, the hole is drilled through to the correct size to match the tap size, for cutting new threads. The tap cleans up the threads, clearing the old steel that is remaining. If the original 1/8" hole is off center enough to make it a sloppy hole, an insert can be installed to hold the new stud. 

     The local VW dealership started sending their broken stud heads to me for repairs, and eventually started buying long blocks from me. Many times since then I have run into broken studs on all kinds of repairs, and they never fool me any more. 

  • Like 5
Link to comment
Share on other sites

Yes!

Link to comment
Share on other sites

The trick is to get the hole exactly centered.

 

Thanks for the tip. Any advice on how you did this?

 

P.S. 3000 engines in 5 years. That's a little over 1 1/2 engines per day, 365 days per year. Wow!

 

 

Link to comment
Share on other sites

 

To support what you have described. 

A member just fought a bunch of broken studs on a 35 Lincoln. Good write up with pictures here.  He also describes use of a Transfer Punch to get the exact center of the hole. 

 

 

 

Link to comment
Share on other sites

How do you get a pilot hole perfectly centered? I would file the top surface flat, to start. Then with a center punch make a new dimple at the center. If you miss the center on the first try you can tilt the punch and rap it again in the direction of the exact center (of course, this is by eyeball). You can actually walk a dimple around a bit till it looks good. Then give it a final rap with the hammer to assure a clean start to the drill.  Since the heads were magnesium alloy, they were softer than the steel studs... so, if the drill wanders and hits the magnesium, it will skew off and ruin the job. That is why the 1/8" pilot hole is started, to prevent drill bit wandering. 

     Another problem that I would encounter with VWs and the 912 Porsche engines is the cylinder head studs pulling out of the case, making the cylinder heads loose. Often, a customer would drive their car to the shop and wait while we installed a fresh engine. I remember a customer bringing his VW  up the drive, and I could tell at a distance exactly what the problem was, for loose cylinder heads created a distinctive blap-blap popping sound. There actually were new, self tapping head studs that could be installed, even with the engine in the car. But the ideal way to fix the problem was to install "Case Savers", which were inserts that fit the thread size of the original studs (much better than helicoils). VW actually began using these inserts at some point... maybe about 1972? It got to the point that I would drill and tap holes for case savers on EVERY engine, and never had a problem with the case savers. 

     Makes me think back to some of the work that we did. When a customer had a bad clutch, I had the boys pull the engine, install a new disc and the person would be on their way in 15 minutes. Did that many times.  I charged $50 for this, and gave that to Johnny and SA, for they did the work. Now, that was a satisfying feeling... 

Link to comment
Share on other sites

I didn't read all this so maybe I'm repeating. 

A stud more or less broken flush we extracted by welding a flat washer through the center hole to the stud and then welded a nut to the flat washer ..Then unscrewed the stud.

Easy Peasy.

We used a hight strength welding rod which I can't recall right now and a arch welder..

Learned it a a

seminar 38 years ago..came in handy many times and never failed.! 

  • Like 2
Link to comment
Share on other sites

Welding a nut to a stud is fine when it is an 'unfrozen' stud in steel. I have done that many times, and it certainly is easy peasy. But when the stud is rusted and corroded in aluminum or magnesium, that will never work. The heat from a manifold seems to bake the stud in place, and it will just never break loose. Therefore, drilling out the stud and tapping clean threads is the only way. I have run into similar 'baked in place' broken studs in motorcycle heads. I have a Moto Guzzi that I had to replace 2 studs on... very common with aluminum heads. 

Link to comment
Share on other sites

5 hours ago, Tom Boehm said:

In the first post of this thread, the OP talks about the inevitable failure of an EZ out. Has anyone ever had one of these tools actually work?    I haven't. 

 

Yes, but rarely.

And not on those baked on cases.

Edited by JACK M (see edit history)
  • Like 2
Link to comment
Share on other sites

11 hours ago, Tom Boehm said:

In the first post of this thread, the OP talks about the inevitable failure of an EZ out. Has anyone ever had one of these tools actually work?    I haven't. 

Yes but I was asleep and I was dreaming.

 

Honestly, I've had them work a few times, but not on head bolts.

Link to comment
Share on other sites

A number of times when I had my rebuilding business, I stripped apart engines that had broken EZ-Outs stuck in a broken stud. The first one I attempted to plunge cut it with a cutting torch, and failed miserably. Thereafter, I just scrapped the heads. Reminds me of all the customer induced trauma that I would see on long blocks that came through the shop. One of the bad things about VW engines was that they were so easy to work on, and so many people tried. But, they are touchy to get right. I once saw a case where the 'rebuilder' tried to take the "1 main bearing out with a chisel and hammer (without splitting the case). Needless to say, I had to scrap the case. But, every once in a while a car would come through with the original engine, still running. About 100,000  miles was the limit before a #3 exhaust valve would break , or a rod bearing would go. What a joy it was to tear down a factory assembled engine... it did not happen very often.

As for EZ-Outs, I have never bought or used one, for they are the kiss of death.

Link to comment
Share on other sites

On 6/19/2021 at 8:14 AM, Leland Davis said:

What I would do is to drill a 1/8" hole directly down through the center of the stud. The trick is to get the hole exactly centered. Then, the hole is drilled through to the correct size to match the tap size, for cutting new threads. The tap cleans up the threads, clearing the old steel that is remaining. If the original 1/8" hole is off center enough to make it a sloppy hole, an insert can be installed to hold the new stud. 

   


Did this exact same process the other day with one bolt holding the seat track mechanism on my Skylark. These bolts rust where they protrude past the seat frame and fight all the way out until they break.  I managed to break at least 3 out of eight on the Riviera seats.

 

Filed what was left of the bolt flat and centre punched. Drilled out with a 1/8” drill, then used the correct tapping size drill I keep just for 5/16 UNC. Tapped it out easily.

 

Most difficult part I have in all of this is getting the centre punch in the centre., this one worked a treat!

 

Now if someone could learn me that skill! 😀😀😀😀😀😀😀

Rodney

 

98A14DAC-E819-469D-9160-FD22EDAD58E2.jpeg

73E84B40-6418-46B3-B8EE-252A238446F4.jpeg

Link to comment
Share on other sites

The pilot hole trick is certainly the way to go. Sometimes you get lucky, and are able to get the job onto the milling machine. Then you can end-mill a flat onto an angled break to aid in centring the pilot drill. Especially useful when the stud is below the surface. Some end-mills will leave a dimple, but this can be punched down before introducing the centre-punch. I'm not averse to trying a round or oval burr for a starting cut in the mill, either. Easy-outs can work on finger-tight studs. Which are a rare species, as seizure is the usual cause of breakages..

 

The stud removers/installers shown by 2carb40 above are a very useful tool, despite their tendency to leave three indents if contacting the actual thread. Far more elegant than two nuts locked together. They are not designed for broken studs, though.

Link to comment
Share on other sites

On 6/21/2021 at 4:16 AM, Bush Mechanic said:

The pilot hole trick is certainly the way to go. Sometimes you get lucky, and are able to get the job onto the milling machine. Then you can end-mill a flat onto an angled break to aid in centring the pilot drill. Especially useful when the stud is below the surface. Some end-mills will leave a dimple, but this can be punched down before introducing the centre-punch. I'm not averse to trying a round or oval burr for a starting cut in the mill, either. Easy-outs can work on finger-tight studs. Which are a rare species, as seizure is the usual cause of breakages..

 

The stud removers/installers shown by 2carb40 above are a very useful tool, despite their tendency to leave three indents if contacting the actual thread. Far more elegant than two nuts locked together. They are not designed for broken studs, though.

Just to clarify. The remover I showed is good to take anything out as long as something is sticking out far enuff for it to grab it sufficiently, stud or bolt with head snapped off. I heated broken exhaust bolts to cherry red and vise grips just smeared around shank. Thought Id try the remover. Put the 1/2"-3/8" adaptor on my Snap-on 1/2" breaker bar and turned those rusty, baked in stubs out. Nailhead and str8 engine cover studs have come out with no marks on studs. Im sure with more stubborn items the tendancy to mark is more prevelent, but I like to be clear in my description so I dont discourage folks from trying, as specially with as many issues this has resolved without damage for the relatively low price! Just an additional note. This tool is open on the end, so can be put over the end of a long fastener and used with a box end wrench to grab right at the base of fastener.

Edited by 2carb40 (see edit history)
  • Like 1
Link to comment
Share on other sites

I like that tool Greg shows as well--I have a nice one. It's good about 30% of the time. But on really frozen studs, it's no better than anything else and there's still the risk of shearing off the stud. Ultimately, your best bet is to not break the stud in the first place. Use time, heat, penetrating oil, and patience. My luck has always been that bolts/studs break off flush with the surface and then there's really no option. I've occasionally been able to weld a nut to the stub, but when the studs are really stuck, all that does is break off the stud deeper in the hole. Drilling is the last resort, but for me at least, it is also the most common method.

 

After that Lincoln engine with 40-something broken head studs, I've gotten REALLY good at removing broken studs. I still don't ever want to do it again.

Link to comment
Share on other sites

26 minutes ago, Matt Harwood said:

After that Lincoln engine with 40-something broken head studs, I've gotten REALLY good at removing broken studs. I still don't ever want to do it again.

Like a man who has been to combat you have done your duty and you should not have to repeat the experience. 

Link to comment
Share on other sites

When a complete engine would come into the shop and I had to remove the exhaust manifolds and muffler, I took care to not break the studs. Quite often, the nut and stud would be rusted together, inviting a broken stud. Penetrating oil or heat would rarely work on the tough ones. I would use a nutcracker and split the nut. Once it had split it was easy to remove it. Then, I would clean up the stud threads with a die, and the job was done. Eventually I got to the point where I could save every stud. I wish I had the tool that Greg shows.. this was back in the early 80's and I don't think they were out there yet. To remove the 16 case bolts I would double nut them. Sure would have been easier with that tool.  

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...