You got to be kidding?

[SSDiv6]

Originally Posted by Ed Wright

I'm surprised steel self locking nuts aren't accepted. The recip airplanes (that's how old I am) that I used to work on used them to hold the exhaust on. Silver plated. I still have some. Our collectors don't get as hot, nor nearly as long as the header pipes did at the jugs on those engines (P&W 4360s). I have them on my car, have never had one loosen. Had castle nuts & keys a lot of places, but not at the jugs. I will probably just tig weld mine.

Ed,
The parts I listed are very affordable and the Silver plated ones are still available too.
I totally agree with you, a reciprocating engine generates a lot more vibration than a race engine would. I believe the use of castellated nut and cotter pin is an overkill.
In my years in the aviation business, I have never seen an aviation spec self locking nut come loose.