Lock nut for exhaust

I bought nylon lock nuts for the muffler (because that’s what I took off).

wouldn’t those deformable lock nuts be better for exhaust? wouldn’t nylon lock nuts get soft and (potentially) back out?

I would think the nylon will melt.

Nylon lock nuts are not meant for areas exposed to heat. Deformed lock nuts would work.

If they really were nylon, then nylon replacements would work. OTOH, the polymer may have been something else. Why do you believe the original locking feature was nylon?

Nylon is a thermoplastic with a melting point below 550F, and will deform (become “plastic”) at lower temperatures. It is not appropriate for exhaust systems.

@jtsanders the nut had a blue liner visible from the top (I figured it wasn’t threadlocker because there was so much… hmmm…). that and being naive, I concluded it was a locknut with some sort of plastic inside.

… but the vibe I’m getting says to just go get one of those deformable ones, case closed… but if there are special locknuts with high-T plastic inside, that’d be interesting to know.

I agree, you should get the deformable metal locking fasteners since they are so easy to find. There is no need to turn it into a science project.

It might just be easier to get OEM replacement nuts from the dealer’s parts window. It’d only cost a few bucks, and then you’d be able to sleep soundly knowing you had the correct nuts. A good nights sleep is important too.

My expertise in the mid 1970s when I worked at the GM dealer was exhaust systems. I never encountered anything plastic.

I agree not to use the nylon lock nuts. It doesn’t take long for rust to set in and lock the nuts in place.

and red threadlocker - overkill?

copper anti-seize on the threads only, or would it be good to coat the exterior too?

I like serrated flange nuts for locknuts in high temp areas. The serrations grip the part and resist rotation. They are easy to spin on and the nuts don’t damage the threads. Copper anti-seize can be used on the threads only for easy removal. Red loctite would be useless. Heating it is how you get the red loctite to release.

anyone know where to get stainless steel M8 1.25 pitch “tension”/“oval” lock nuts (not nylon)? I tried:

Home Depot
Bolt Depot

… the closest thing I found was Home Depot (or Porsche) but they have zinc plating only. McMaster has a “flex top expanding” lock nut in 18-8 SS but it’s about $5.00 per nut!!!

The dealer has got to be cheaper. If Fastenall doesn’t have it, it doesn’t exist.

"anyone know where to get stainless steel M8 1.25 pitch “tension”/“oval” lock nuts (not nylon)? "

Whenever I want stainless steel fasteners, I go to a marine supply store.
I can’t guarantee that they would have the exact lock nut that you are looking for, but I think that a marine supply store would be your best bet. Just be prepared to pay a lot.

yeah, we used tons of stainless stuff when I built yachts

Flat washer, split washer, nut. Stainless if you like. But what’s the big deal it’s not like your are going to be taking this off very much. Are you?

If you’re worried about this, I’d skip the lock nuts and us a jam nut, 2 of the same nuts, tighten the first one, put on the second, tighten it, you’re set.

Actually, I never used a lock nut or stainless nut on an exhaust system. A single nut corrodes up quickly enough to lock itself in place!

Yes, @texases. A jam nut seems such an easy and certain solution.

I often take a small punch and mar the threads of a bolt, or the end if it doesn t protrude, if im worried about a nut backing off and don t have room for a jam nut. you can still remove the nut, but it won t come off by itself