Fasteners on exhaust systems

[Lubener]

Originally Posted By: 28oz
Originally Posted By: Lubener
Originally Posted By: 28oz
Right or wrong, I've always used grade 8 hardware when replacing anything exhaust-wise. Never had an issue with it.


Most shops use grade 2. I never heard anyone having issues with exhaust fasteners breaking on their own.Maybe after many years.


Grade 2? Might as well use zip ties! Joking..... I use grade 8 'cause if it's worth doing, it's worth over-doing.

The u bolts on the clamps are no better than grade two. Try breaking a 3/8 grade two bolt, you won't do it w/o an impact. If grade 8 makes you sleep at night, sweet dreams..

 

[greasegunn]

Thanks for all the responses. If a different metallurgy is used on the fastener than the system, does a difference in the thermal expansion properties make a difference?

 

[SHOZ]

Stainless steel nut and bolt may gall on exhaust. I use a 316 SS bolt and grade 8 nut. The nut may rust and the OD change but won't gall on the threads.

 

[Kestas]

Originally Posted By: greasegunn
If a different metallurgy is used on the fastener than the system, does a difference in the thermal expansion properties make a difference?

No, it's not significant.

 

[eljefino]

As others said, use cheap hardware and antisieze. I've busted 5/16" exhaust bolts with only an 18" breaker bar. Consider them "consumable".

 

[greasegunn]

Originally Posted By: eljefino
As others said, use cheap hardware and antisieze. I've busted 5/16" exhaust bolts with only an 18" breaker bar. Consider them "consumable".


Wouldn't think of reusing a fastener in this application here in the rust belt. Not that expensive to worry about.

 

[SHOZ]

If it's a nut and bolt no big deal. If it's a stud then yes big deal.

Hyundai decided to use a mild SS for the exhaust manifold and SS turbo mount bolts and studs. Bolts come apart but the studs usually seize and break off or strip the threads in the manifold.

By mild I mean they all rust and it looks like cast iron but is non magnetic.