I noticed last night that when I mount my headers in place the exhaust studs are too long...well they have a skinny unthreaded area in the middle and the nut would bottom out before touching the header flanges. If all nuts were tight the header would still not fit tightly to the block. Here's a pic..

Doug C

another...

You get to install new exhaust studs!! the stud you pictured is shot

that necked down area could have been a result of the nut being loose, and the flange moving around and wearing the threads off...or rust and corrosion, or a comination thereof.

Tim, it really looks like they were machined this way, all of them are the same. Maybe the original 911's heat exchangers had thicker mounting flanges or something? I will definately replace are of them though...but with what?

Doug C

The 3.0s had a thick/thin flange difference.....but those studs look to be in need of replacement.

Yes, I will be replacing ...but again, with what???
If I get the same ones (new) they will still be too long for the bursch flanges. Maybe theres a fully threaded stud I should use? BTW, it's a 2.7

Doug C

Easy to figure out. Measure the depth of the stud hole, the thickness of the exhaust flange, exhaust gasket, the lock washer and nut. Add 2-3 mm so that you have minimun of 2 full threads showing after everything is tightened up. Call your local Caterpillar dealer, chances are they might have the studs in stock or can get them in next day.

There's a lot of bogus / fake fasteners out there, most from China, Korea, etc.

Caterpillar makes all of their own fasteners, when they grade them, they all exceed specs. I've been to their metaluragy labs. The prices are great. Most of the fasteners I've replaced on my 6, bike, and RS are Cat.

One of the best thing I like about their bolts is the head is about 30% thicker, less chance of busting your knuckles when the wrench slips off, damn I hate that.

Anyway, give it a try, I think you will be pleasently surprised. Later, Don

Use the ones you have to come up with a length. They are 8 mm diameter. You can buy them at any parts store that deals in VW. Your biggest challenge will be removing them all without breaking any. Go slow.

Doug,
The thermal reactors used on the 2.7 required a thicker flange. You can get a good set of studs to replace them by going to Metric and Multistandard in Irving.
They are right near Texas Stadium. They have the correct studs in stock. They also have a 25.00 minimum purchase for credit cards. Either take cash or stock up on other stuff while you are at it.


I went there yesterday. Didn't have cash, and the closest ATM is in a Topless bar on Harry Hines blvd. I would be getting serious from the wife if I got money out of an ATM in a topless bar.

Oh.. and the easiest way to remove the studs is to weld a nut onto them and unscrew them from the head.

Yet another case of wild speculation coupled with flat out wrong answers. Those are 2.7 studs, nmade that way. They're for the the TR flanges, and look to be in good condition. My PET isn't loaded in the new computer, so I can't give you the correct length, but I'd guess about 30mm, maybe 35. You don't want them too long, though. The Cap'n

the PET wouldn't help you, i'm afraid because of how metric threaded studs are specified. i found this How Metric Studs Are Specified PDF from Maryland Metric interesting and helpful.

PET properly calls that stud 22mm (25 in the case of 911T, for no reason they explain...) but as shown on the "How Studs Work" document, the unthreaded area is NOT included in the stud spec ! the drawing in the doc shows how to calculate the length of the unthreaded area, and thus the overall length of the stud...

in this case it seems to be 10mm; when this topic came up on the 911 list, the consensus was that the proper studs for an early exhaust car should be 32-35mm measured OAL, as you mentioned.