I am currently in the process of changing manifolds on a friend's '74 Duster. When I laid out all of the mounting hardware, I noticed that all of the nuts are "regular" brass nuts. According to all of the resources here, it would seem that the nuts on the front and rear studs should be a domed lock nut. After digging through the forums for some time, it seems that nobody has come up with a source for these. From what others have posted, I assume these nuts should look like this:


Others have recommended castellated nuts, but the factory originals do not seem to be designed for a cotter pin retainer. Does anybody know how the original nuts were supposed to work? What material were they made of? I have found another supplier that manufactures nuts which look more similar to the factory ones, but I want to know that these work the same way before I order them...
http://www.locknuts.com/dome_flex.html
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The matching brass washer has a counter-sink on one side of the ID.
The slotted / taper feature on the end of the special nut, fits into the washer's counter-sink, which compresses the end of the nut, to grip the stud so the assembly does not loosen with heat cycles and vibration.
The nut itself looks to be mild steel.
DD

I have the special washers for the front and rear studs (although they are a little chewed up). Is it better to attempt to replicate the OEM configuration, or is it better to simply re-engineer this system?

I would think that using any "prevailing torque locknut" and a washer (to allow manifold movement) should be sufficient, but I am curious to hear what others' luck has been using such an arrangement.

I imagine that the OEM nuts are no longer available, and 30 year old used ones probably won't work to factory specs anymore...

I bought normal tapered castle head steel nuts at the hardware store and used them with the brass washers on the (2) fore and aft manifold studs. You use a cone type washer for the center stud. All other nuts are brass so they don't rust onto the stud over time.

They look good and work well to allow a snug fit but allow the manifold to move around as needed during the heat cycles.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

So, the best bet is to use the castellated nuts with the "teeth" facing the washer on the front and rear stud, correct?

Correct! The head when installed backwards centers the heavy brass spacer/washer.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG