Stud Stripped its Hole

[OsoMoore]

It's not my fault! Ok, maybe it is. But that's not the point.

I tried to put on a nut, and it started spinning its stud before hitting the torque spec (18 lb/ft). Then I tried remove the nut, and it is still just spinning its stud. The nut does not move further out, it spins the stud along with it, and I can't seem to work it free with lock pliers.

Now I have a chain housing attached with a nut that can't tighten and won't back off/out either. How do I remove the nut, and/or extract this stud from its stripped hole? And how do I move forward afterwards?

[PeteKz]

Keep turning it, and pull outwards as you do. It will eventually come out. Then Timesert/Helicoil the stripped hole and reinstall. And make damn sure your torque wrench is accurate. 18 Ft-lb is the upper spec. For M8 nuts/studs/bolts, the usual spec range is 15-18.

[TimT]

Is that a lock nut?

[TwoBluPorsches]

Got a welder ?

All of the things that I can think of end up with the likely use of a welder to extend the stud so it can be worked out.

The working out portion may involve making a little puller tool.

Once the stud is out, the messed up threads /hole will end up with an insert.

I had a 2.7 mag case with basically every threaded hole fitted with an insert. It just got to the point where it made sense to do that ahead of assembly so I didn’t have the stress of worrying about a fastener making it to torque.


I’m curious what gets suggested and how you eventually solve this problem.

[OsoMoore]

Originally Posted by TimT

Is that a lock nut?

Maybe part of the issue is how I interpreted Wayne's book "Use the factory 13mm nuts on the studs... [that] are egg-shaped locknuts that resist vibration." I used prevailing torque nuts here. I put one on and torqued it originally without issues. Then took it off to redo a chain route. Then I put a fresh one on. I did not pass the torque spec, however, it stripped before I hit the torque. So maybe I'm not to blame?

Originally Posted by TwoBluPorsches

Got a welder ?

All of the things that I can think of end up with the likely use of a welder to extend the stud so it can be worked out.

The working out portion may involve making a little puller tool.

Once the stud is out, the messed up threads /hole will end up with an insert.

I had a 2.7 mag case with basically every threaded hole fitted with an insert. It just got to the point where it made sense to do that ahead of assembly so I didn’t have the stress of worrying about a fastener making it to torque.


I’m curious what gets suggested and how you eventually solve this problem.

I'm not surprised it happened at some point in this rebuild. At least it wasn't a base case closure location. I'll dive in tomorrow morning. I sense another PP order...

[OsoMoore]

I don't see any inserts on PP except for head studs. Any recommendations for a little m8 like this?

[OsoMoore]

I couldn't find anything on our host.
Maybe something like this?
https://www.mcmaster.com/90025A113/

[OsoMoore]

Found the Time-Sert site, looks like that is the gold standard.

I guess I need to get the stud out and figure out what is the appropriate depth. Yay!

[draw]

Yes, use time-serts. Depth for an M8 stud is 16mm.

[john walker's workshop]

Maybe the nut threads stripped and not the stud. Wrong nut anyways. Use a normal nut.

[smadsen]

Grab the nut with a small channel locks or pliers. Pull back on the nut as you turn it counter-clockwise. The striped threads just need a little help coming out.

Otherwise use a Dremel & cut a slot in the stud for a screwdriver. Hold the stud, spin the nut.

[proporsche]

i would use butane torch heat it up should come off, after inspect and use only regular nut and wave washer not spring and not locking nut

Ivan

[David Inc.]

Originally Posted by john walker's workshop

Maybe the nut threads stripped and not the stud. Wrong nut anyways. Use a normal nut.

I'm really curious about this one. I stripped one of these studs trying to use prevailing torque nuts as well because that's the nut that was on the block originally. I think it's also called for in the PET, but the crankcase page in the PET is confusing and boy does it ever not feel "right" putting that nut on at that torque.

To OsoMoore, I called Pelican to get the right stud and they gave me part number 99906207302, which is an M8x16. The PET calls out an M8x20, but best to check once you have the stud out. Yours looks like mine, though, where the threads don't stick out past the end of the nut.

[OsoMoore]

Originally Posted by David Inc.

I'm really curious about this one. I stripped one of these studs trying to use prevailing torque nuts as well because that's the nut that was on the block originally. I think it's also called for in the PET, but the crankcase page in the PET is confusing and boy does it ever not feel "right" putting that nut on at that torque.

To OsoMoore, I called Pelican to get the right stud and they gave me part number 99906207302, which is an M8x16. The PET calls out an M8x20, but best to check once you have the stud out. Yours looks like mine, though, where the threads don't stick out past the end of the nut.

I did a quick measure this morning before work. The stud sticks out about 1 inch, which is 25 mm, but given I was measuring over the nut and the bag-covering, it could be 20 mm.

Given the proposed 16 mm "depth", I summarize the entire stud should be 35 or 40 mm in length.

I'm going to wait to order the Time-sert kit until I actually get the stud out, and didn't have time to work at it this morning.

[draw]

According to the PET, the correct stud in that position is M8 x 20mm. Porsche followed the DIN 835 standard for the studs, so 20mm is the nominal length and the total length is 36mm. The part number 99906207302 is not correct. You can use part number 99906200603, but it is 1mm longer at 37mm. Belmetric carries the correct DIN 835 length stud if it matters.

See my post below for more information...

Originally Posted by draw

I believe that most, if not all, of the studs in the case are DIN 835 standard. This means that the "tap" end is 2x the diameter of the stud. For example, an M8 stud has a tap end of 16mm. This is the end that is screwed in to the case. The other end is the nominal length of the stud.



You can identify the stud from the parts catalog...



Pos #4 on the parts diagram is an M8 x 35mm stud.



So, the height of this stud in this position is 35mm.

Some words of caution...First, there are mistakes in the parts catalog, so be careful. Second, most of the studs you can buy are not DIN 835 and will not match exactly. Meaning, that the nominal length of a stud might be 35mm, but you may only be able to find it in 36mm. Third, a lot of these motors have been apart a few times by now and may not have the correct studs in them to use as a reference. I crosschecked all of mine against the parts catalog.

I measured and took pics of every stud in my case before I removed them. If you post a pic of the missing stud, and I might be able to help you.

[OsoMoore]

Originally Posted by draw

According to the PET, the correct stud in that position is M8 x 20mm. Porsche followed the DIN 835 standard for the studs, so 20mm is the nominal length and the total length is 36mm. The part number 99906207302 is not correct. You can use part number 99906200603, but it is 1mm longer at 37mm. Belmetric carries the correct DIN 835 length stud if it matters.

See my post below for more information...

Thanks for the detailed info and analysis, I appreciate your knowledge a lot! I'll get the right stud and hopefully can do the work next weekend, along with cams!

Meanwhile I have plenty of small things to clean while I wait for shipping.

[OsoMoore]

It was NOT the hole that stripped, but rather the end of the stud. Probably torn up one two many times by my re-applying of that nasty nut.

Its neighbor also seems to be damaged, so I suspect I should replace both.
What's the preferred way to get these guys out? Double nut and push hard? Pick up a torch at HF and apply some heat first?

[proporsche]

use heat and just clean up the upper threads ,do not go to crazy about the 18pounds 16 is just fine
Ivan

[David Inc.]

A stud extractor worked fine for me with a bit of heat. The style that's a three-prong gripper in a chuck.

I'm happy to be wrong about the part number, but the 99906207302 stud was what I was given to over the phone from pelican and it matched existing. To be fair they said they weren't 100% certain themselves. YMMV.

[yelcab1]

After hanging around aircool engines for years, I broke down and got a set of Stud Extractors Collets. That would make this an easy job.