Exhaust Studs...Just venting!!!

[gt3r]

I just finished drilling out 12 exhaust studs that all sheared off due to corrosion, when I was trying to remove my heat exhangers on my 85 carerra. I just don't get it....$750+ stainless heat exchangers bolted to $.29 regular steel exhaust studs?!?!?! Couldn't Porsche have used a higher quality stud maybe even stainless???? Anyway, this horrible job only ranks second to sanding bottom paint off of a boat. Anyway just my $.02

[Rot 911]

wow, can't believe you broke all 12 of them. did you check here first for suggestions as to how to remove them, such as using heat?

[john walker's workshop]

welcome to the board. if you search the archives, you will never have to go into a job blind again.

[Jim Sims]

A look in the archives will result on the knowledge that the application of a acetylene torch to the nuts and studs to the point where they turn cherry red will often prevent this (but not always). On occasion just getting the torch out at the first hint of a stubborn nut will cause it to loosen . In all seriousness, I'm sorry to read about your grief with your car's exhaust studs. Stainless steel fasteners have their problems too; the standard grades are considerably weaker than carbon steels plus stainless steel threads are subject to galling and welding if lubricant is lost. There are exotic fastener alloys such as MP35N which are very strong, heat and and corrosion resistant but the are as expensive as sin (the 35 stands for the 35% cobalt) with the base metal costs starting at $25 per pound before processing. I have had non-galling silver plated or tungsten disulfide plasma coated bolts made from this material that cost $150 each due to the material cost and processing expense (strong equals hard to forge and machine). However, with a larger order the cost might go down to say $50 per Porsche exhaust stud; would you be willing to pay $600 for a set of exhaust studs? Probably after drilling out 12 of them you might. If a whole engine was built this way it would get very expensive though; its all about trade-offs. Cheers, Jim

[gt3r]

Oh I got all of the nuts off without a problem by using a torch but once the exchangers were off, most of the studs were severely rusted to the point that they needed to be replaced. That is where the trouble started. I tried to use heat, penetraing oil to ge the studs out but not luck. I tried to use a collet type stud extractor and even welded nuts onto the studs to try and extract but no luck. I guess after being in there for 17 years, they weren't ready to come out. Believe me I did research various methods of stud extraction but nothing seemed to work. Thanks for the replies.

[rraynman]

So, I am basically in the same boat or going to be very shortly. I only have six studs to worry about this time because I am only removing one heat exchanger to replace leaking oil return tubes. But I would like to replace my exhaust studs with something better than stock because I plan to upgrade to SSI H/Es in the near future.
What did you replace your exhaust studs with? Did you use anything special that won't corrode so much?
I probably would pay $600 if it meant that I could pull my exhaust off in a few minutes without worrying about broken studs.

[Wayne 962]

As they heat and cool, and heat and cool, the temp cycles temper them and make them brittle. Use anti-seize on the threads to prevent this from happening again.

Unless the studs are really, really gone, I don't recommend replacing them...

-Wayne

[gt3r]

I tried to find stainless studs to use but I was unable to find the correct size and length so I ended up using steel studs and I used a copper based anti-seize on the studs and exhaust nuts. I don't drive the car in the rain so after a couple of months the studs still look new. I'm not sure how soon they start rusting after they get wet. Hope this helps. P.S. I agree with Wayne, if the studs are in fairly good shape, LEAVE THEM IN.

Mike

[rraynman]

Thanks guys.
I have already snapped one stud. I am really not looking forward to dealing with it after everything I have read.