Mid 9, Stripped studs, Oil leaks, Fixable?

[74cookiecutter]

Well, I over torqued a nut on the oil sump plate as part of my five year oil change program and stripped a stud.

See the long stud with all the threads showing? That one was done before. I added the one two over from it.

The first stripped stud I found was on the Chain cover where one of the A/C mounting bracket bolts was over tightened. See the far lft stud with three washers.

Now I have three studs needing repair.
Can I fix this unfortunate situation easily? Will it require re-taping the block?
Do "they" make a stud with a slightly larger diameter on one side to go into the Magnesium block and the correct dia on the other end???? please say they do!

[exhaustfumes]

get a stud extractor and pull them, and put in new studs. good as new.

[74cookiecutter]

Unfortunatly, it's the magnesium that is stripped out of the block, not the threads on the stud. I might need a stud extractor one day though, at this rate.

[Jim Sims]

Have you stripped the stud or the tapped hole (in the engine case or chain case) the stud goes into?

[74cookiecutter]

The tapped holes. When I removed two of the studs I found soft metal between the stud threads. I feel sure the magnesium threads from the block are stripped on these three studs.

[Jim Sims]

A "Helicoil" thread insert is probably a good fix for these striped studs as they normally see little load. On the sump stud area I'd check the material thickness to ensure there's enough stock for the helicoil tap. Be very careful drilling with the helicoil tap drill as the magnesium is like butter (a drill stop - a small locking collar that limits drill pentration - on the drill bit is in order). Both of these repairs (sump and chain case) likely could be done in place. If you haven't done a helicoil thread repair before you may want to consider obtaining some experienced "hands on" help.

[klaucke]

My 74 had the same problem. I used a 7mm stud to replace the 6mm stud, with the same thread pitch. I bought a 7mm bolt and cut the head off. It works perfectly fine, it sees very little torque. With the 7mm stud, the tap cuts very little material (although there is plenty of material surrounding the studs regardless). A Heli-Coil is another alternative, only it is overkill for this situation in my opinion and can always be done at a later date after you have used a 7mm stud.

You may have to file the sump plate hole a bit to clear the stud.

[74cookiecutter]

Jim, I like the idea of a Helicoil anchor system. You mentioned "they normally see little load" but how much load will this Helicoil system hold? I am concerned about getting the holes tapped straight and at the correct depth given the awkward locations(under the car and rear brace in the way of the chain cover). What do you thik about J. K.'s suggestion of using a 7mm? Wish someone made a 7/6 combination stud.

[bigchillcar]

anyone know the proper torque for these studs while on topic?
ryan

[Doug Steinel]

8 ft-lbs

[Jim Sims]

Given that the magnesium base metal shear strength is likely the limiting factor in this case, a proper Helicoil repair will typically be stronger than the original tapped hole. Drilling the tap drill hole normal to the surface by hand is always problematic but to do something else will require a custom made drill jig with bushings or taking the case apart and putting it on a machine tool. Use a drill stop collar to limit the depth drilled. A right angle drill with variable speed control is helpful (perhaps essential in the repair of the chain case). IMO making a 7 mm tapped hole is about as much trouble as installing a 6mm Helicoil repair. Accessing the chain case for the repair will likely require removing the rear piece of engine sheet metal, the chain case cover, oil line to tensioner and perhaps the the rear engine mounts (support the bottom of the engine with a jack stand or blocking).

Being a big guy, I tend to hold the wrench or ratchet right at the fastener end when tightening small fasteners; this way my ability to overtighten and "strip" is limited by poor leverage.

[bigchillcar]

when jim speaks, i listen..
ryan

[Nine9six]

Jim is spot on...Don't worry so much about drilling straight, as the drill will follow the existing hole, just go slow and easy. Do not drill any deeper than the existing holes and do not over torque during reassembly.

[Jim Sims]

See below for an example of a drill collar or drill stop; most good hardware stores carry them.

http://www.climaxmetal.com/Drill_Stop_Kit.htm

[74cookiecutter]

Jim who carries the Helicoil product line? I'm in Little Rock, AR so specialty fastener shops are not an option though a construction supply house might have access to them.
In any case; What Helicoil product do you recommend for this job? i saw SS and other coated products plus tabless coils... Too many choices.

I was thinking that J.K. was not retapping the hole, rather he just forced the 7mm stud to tap its own way into the existing stripped hole. If I have to tap a 7mm you're right and I'll just stick with the 6mm and tap the block to receive the Helicoil.

[74cookiecutter]

Nine9six,
Where did you hear the phrase, "they don't care that you know, until they know that you care"?
I had heard that phrase in my early sales training days from a very talented sales director/manager who is now retired.

[74cookiecutter]

Doug, do you have a ref source I can get my hands on for all the torque requirements on these cars?

[Jim Sims]

Having lived and worked in Eldorado for a while I know about the difficulty of finding anything specialized in Arkansas.

I would suggest ordering the below kit from McMaster Carr, the 18-8 stainless steel with a tang is fine. Don't bother with the tang removal tool, a slender pin punch can be used to break the tang off.


91732A947

[Doug Steinel]

For engine fastners like the sump pump nuts, I use our host's "How to Rebuild and Modify Porsche 911 Engines." Porsche also has small (about 3x5 in.) books which give specifications like torque settings, etc.

[Rot 911]

Originally posted by 74cookiecutter
Jim who carries the Helicoil product line? I'm in Little Rock, AR so specialty fastener shops are not an option though a construction supply house might have access to them.
In any case; What Helicoil product do you recommend for this job?

I live in a town much smaller than yours and my local Ace hardware carries helicoils. If you can't find them you can get them from an online store in just a few days. "Helicoil" is the brand name. You just need to get the 6mm helicoils. Very easy to install. Take you maybe 10 minutes.