Exhaust Manifold Stud Installation

[Michael G.]

Re: Exhaust Manifold Stud Installation

Today's zinc-plated lock nuts also tend to gall stainless because zinc's friction is very high and they don't have a measured amount of lubricant on the deformed threads, (if they have any at all, which is probably not the case). The standard lock nuts GM used back then were cadmium plated, then dipped in wax, then tested to make sure they had consistent friction. Additionally, those were intended for low-friction un-plated carbon steel studs. It made for consistent tightening at low friction, what you need with a lock-nut.

Those nuts, if you could get them, (you can't) might not gall the stainless.

You are better off using doubled-up zinc plated normal nuts, as Tim suggested, or, alternatively use two brass ones. Anti-Seize is a good idea on both ends of the stud.

If you're going for max judging points, run a tap through the lock-nuts, use anti-seize, double them for normal use, and remove the outside one for the judging field.

[Stephen L.]

Re: Exhaust Manifold Stud Installation

However, I think the original style, steel locking nuts would work OK.

With respect to "locking" nuts - my version of 341003 (which appear to be original ... or original looking) are not "locking" in the sense of having some kind of nylock or equivalent - in what way are these self-locking? - in removing them a little while ago, there was no lock washer either...so how do they stay on (apart from rusting on )

thanks

[Joe L.]

Re: Exhaust Manifold Stud Installation

With respect to "locking" nuts - my version of 341003 (which appear to be original ... or original looking) are not "locking in the sense of having some kind of nylock or equivalent - in what way are these self-locking? - in removing them a little while ago, there was no lock washer either...so how do they stay on (apart from rusting on )

thanks

Stephen-----


The original nuts are what are called "flex-top locking nuts". This type of nut provides a mechanical type of locking. Distorted thread locking nuts can also be used but are not what was originally used. Either of these type of nut will provide FAR better locking than any sort of lock washer. Most lock washers are virtually useless at threadlocking.

Nylock lock nuts cannot be used on the exhaust studs. These things get way too hot for the nylon to survive.

[Stephen L.]

Re: Exhaust Manifold Stud Installation

thanks Joe

never heard of a distorted thread locknut - good to know


A distorted thread locknut, is a type of locknut that uses a deformed section of thread to keep the nut from loosening from vibrations or rotation of the clamped item. They are broken down into four types: elliptical offset nuts, centerlock nuts, toplock nuts and partially depitched (Philidas) nuts.

[Tom P.]

Re: Exhaust Manifold Stud Installation

Joe,
GM cars of the 60s-70s (and maybe others) used a nut on the transmission cross member where it attached to the side frame rails. This nut I'm referring to is of the self locking type (partially distorted on one end of the nut). Could this be the same nut as used on exhaust studs? Or, SIMILAR enough to be accepted?

[Joe L.]

Re: Exhaust Manifold Stud Installation

Joe,
GM cars of the 60s-70s (and maybe others) used a nut on the transmission cross member where it attached to the side frame rails. This nut I'm referring to is of the self locking type (partially distorted on one end of the nut). Could this be the same nut as used on exhaust studs? Or, SIMILAR enough to be accepted?

Tom------

The exhaust stud nuts were a little different. They had tiny "slots" on the outboard end of the nut. These were very slightly "pinched in" during manufacture and create the friction lock.

I believe the type of nut you are referring to is the standard distorted thread nut, often referred to as a "Stover" nut. These were used in several places on a Corvette. C2 and C3 upper a-arms were one place. Some engine valve adjusting nuts were also of this type. They would work OK on the exhaust studs. Whether some eagle-eyed judge would detect them, I don't know.

[Tom P.]

Re: Exhaust Manifold Stud Installation

I finally dug through my stash of nuts and found these. I THINK (not sure) that I've pulled these off of Chevelle transmission cross member attaching bolts.
Are any of these the style of self locking nuts which would have been on exhaust manifold studs?

[Joe L.]

Re: Exhaust Manifold Stud Installation

I finally dug through my stash of nuts and found these. I THINK (not sure) that I've pulled these off of Chevelle transmission cross member attaching bolts.
Are any of these the style of self locking nuts which would have been on exhaust manifold studs?

Tom------

These are a Stover-type lock nut. They are not exactly the style I've seen on the exhaust threads. I believe the exhaust stud nuts were the style with small "slits" around a very short extension on the top. These would work OK on the exhaust studs, though.

[Carl N.]

Re: Exhaust Manifold Stud Installation

Agree with Tom, after many years of turning wrenches on industrial equipment, stainless on stainless equals galling. With care you might use 303 or 304 ss on 316 or 321, but be careful.