I thought it was the nut that was coming loose. It turns out the stud will not stay tight resulting in a leak. What can I do to keep the stud in tight? Would it be too hot for locktight? What are my options other than tightening it down till it breaks.

Put a little JB Weld on the threads. The heat will not make the JB very strong but it should hold it in until you need to remove it.

Is that an aftermarket lock nut? If so, that's your problem. Get the right nut on there and the stud should stay in...

Sorry, I don't think so. The glue will break down with the heat. Probably time for an insert.

JB weld will not work, and he is not at a point of desperation. Since he has a 8mm stud coming out he can go up to a 10x1.5-8x1.25 step stud.

A Time-Sert is also an option.

If he tries the JBWeld it will fail and make the workable repairs listed above much more problematic.
Good luck!

This happened to me on 3-4 of the studs. I bought new ones then cranked em in there real tight. I was way too nervous to put lots of torque on the old studs. Now I have some new, some old studs, with spares to replace the old ones when they come loose. Eventually, every part on my 914 seems to come loose and need attention
I will be back under there replacing the poor "seal" I made on the stubs to my header this weekend and will check on my fix(es) while I am down there.

What engine?

The Cap'n

Type IV

Oh. One of the common issues here is the integrity of the boss on the head. Exhaust port cracks can intrude into the boss, or they can otherwise weaken the material in that area. I could attempt to install an insert for you, but it has been my experience that you have about a 50/50 chance of saving it. Used to be an easy fix, back when all the heads had a few miles on 'em. Now, not so much. There is NO easy magic fix. None.

The Cap'n

The Cap'n may be right. If the stud pulled out of one of the inner bosses (closest to the center of the engine) then it is entirely possible that the stud pulled out because of a crack. They radiate from under the ex valve seat out to the stud boss. It's pretty obvious when that is the case as you can get a good look at once the exhaust is off. If that is the case it's time for the heads to be re-worked, or tossed.

If it pulled out of one of the outer bosses the likelyhood of a crack precipitating the failure is extremely remote.

The stud didn't exactly "pull out". It was just loose. I tightened it about a week ago and it came loose again. I went to NAPA and found an M8, 1.25 X 50 stud, put it in, tightened it down and now we'll see how long this one lasts. Thanks for all the help.
Cheers, Elliot

My .02C.
First get the right exhaust nuts. That looks like a lock nut. And its rusted on. On the new nuts use copper based anti-seize. That way they will come off the right way. Nut first, not stud and all.
I like you just went to NAPA and put in new studs. They've been holding fine in both 914 engines and the 911 engine.
If the threads are trashed you'll have to do inserts.

That IS a copper exhaust nut. It wasn't rusted on. It came right off the stud.

First of all, those are NOT "copper exhaust nuts" They're "copper PLATED steel self locking nuts". I don't understand why this bogus belief won't go away! Locking nuts have no place on exhaust studs on a Porsche air cooled engine. They were readily available when the cars were built, but the engineers at Porsche and VW chost not to use them. I don't either, having seen too many problems related to their use in this application. They're fine on water cooled applications, and both VW and Porsche used them in those apps.

The Cap'n

This is the type I use.
http://www.pelicanparts.com/cgi-bin/smart/...76%29%2C%20Each

Just because Pelican sells a BMW part (that's what they call it in the catalog) that they say fits a 914 doesn't make it right for your application. I repeat, Porsche and VW chose not to use self locking nuts on the exhaust systems of their air cooled cars, notwithstanding the availability of such parts. You don't NEED locking nuts on the exhaust. People use split lock washers there, too, despite the fact that it's a widely accepted fact in the industry that they have no place in the exhaust system. Go figure.

That said, you're free to put anything you want on your car, right or wrong.

The Cap'n

I'll second that! I hate the damn things and also feel that they have no place on these engines. They cause way more trouble than they prevent.
On my race heads I use the internal wrenching 911 ex nuts.

And I should also add that it is not possible to use to much anti-seize down there. I slather it on the studs before I screw them in the heads and slather it all over the studs and the nuts. I prefer the copper based stuff as it handles the heat better than the silver permatex stuff.

I know NAPA sells copper based and I imagine that some other FLAPS do to.

OK, Cap't and Ham. You both mention that those nuts cause problems but would you mind enlightening us dumbasses just what those problems are? And El Liot, mine did the same thing last year before RRC. I Helicoiled mine and then made the mistake of posting it. Turns out the crowds favorite is a timecert or something similar to that.

Heli-Coils are fine.

The clinch nuts drag the stud back out when they are removed. That usually means that aluminum threads are drawn out. Might as well just use a bolt.

I have also had MANY heads that landed in my shop when folks were installing their ex with new clinch nuts on old studs and the studs broke before the nuts got very far up the threads. Now that is not to say that the studs weren't old and flaky to begin with, because they were. But I have also seen them damage the threads on new studs.

Based on first hand experience I am not a fan.

This timely for me as I will be bolting up my ex system in a few weeks. I bolt those new copper clad nuts , should I just use grade 8 nuts and flat washers? Sorry for the HiJack, Elliot.

Pretty much any 8x1.25 nut will do. Any sort of clinch nut is not the way to go IMO.

I am about two weeks out from doing this as well.I just bought a set of the coppers - at least they were cheap.

Capn/Ham - just loads of copper anti sieze, a flat washer and a 8x1.25?

Thanks!

The stock nuts have a slice in the side; they are indeed self-locking. Perhaps not as much as the squashed nuts that are the popular replacement, but they are self-locking. They also have a flare on one end that acts as a built-in washer.

--DD

and all these years I was worried about nothing.

Many moons ago, when installing my Kerry/Hunter header system
with "shorties" "Stubby" exhaust
The headers pipes were a bit big, I couldn't use a nut,
short but quick fix, (I really wanted to hear these headers!)
I used one of my CV bolts,(six side)
used a couple washers,snug it in

I've kept an eye on 'em only time I had to re tight them
was after the first time and the exhaust copper washer settle in.

They stayed in since.
The best part, real easy to reach with allen head socket
no open end wrench

When I had the heads done on a core engine I have I noticed there were 9mm stud holes in the heads. A few of the studs were missing when I got the engine. I found some 8 X9 studs here. http://www.bus-boys.com/heads.html#hardware

My only precaution. They are not straight, Very poor quality. When you lay them on the bench and roll them they wobble. It's hard to get these started and aligned.

I think Chris Foley sells these too. I think I spotted them or someone posted that he does after I bought the ones from the Bus Boys.

I don't mind the hijack. Especially when it includes good information. Wait till I find the bastid that sold me those copper plated nuts. Why I aughta'... Anyway, it's a good thread if I can learn something form it and I have learned lots from this one.
Cheers, Elliot