Securing exhaust manifold studs?

Question

Usually the issue is them getting rusted into place and breaking on removal. Well, I have the opposite problem. Properly installed and torqued studs with nuts are loosening themselves... The nut is staying in the position it was tightened to, but I've had the stud itself walk out multiple times now. It tightens in nicely and will be fine for several weeks. Then all of a sudden it has walked out (I'll find it hanging on by just a couple threads, or like last night where it was just sitting in there all the way out of the threads!).

Book seems to suggest the clean & dry plus torque is appropriate, but that's obviously not working. Are there any high enough temperature, but relatively low removal force (blue at best) threadlockers that can tolerate the heat that an exhaust manifold stud will see?

Answer 1

According to their datasheets Resbond 970TS is capable of withstanding 2100°F

Another method would be the use of locking wire on the studs

Answer 2

If the stud is torque-to-yield by design, you need to replace them with new ones as they have stretched. https://en.wikipedia.org/wiki/Torque-to-yield_fastener

I know that generally in the engine community, they use anti-seize and not thread-locker. Thread-locker over time with corrosion can cause the stud to be permanently seized (regardless of thread-locker strength) causing it to snap on removal when you try to break it loose.

Using lock wire as suggested by @Myself in an answer below would be preferable to using thread-locker but I suggest you seek out the cause of the stud no longer gripping the threads mechanically.

Answer 3

I just couldn't bring myself to spend the $$$ for Resbond 970TS (which also has the downside of a 6 month shelf life). Instead I opted for Rocksett (cheaper and does not have the short shelf life) which seems to be working fine so far. I put it on 5 days ago and have seen no rotation since.