I have roller tip rockers in my 3100 carbed Fiero engine. Had a very curious thing happen. Ran the engine for a while and it developed a miss. Pulled the plugs and #2 was dead. It got spark so pulled the valve cover. Exhaust rocker was backed off and the pushrod had fallen off the rocker arm. Thought, I just forgot to adjust it, the nut was near the top of the stud. Set the lash about one turn down and put it together, ran perfect for like 45 seconds, the clack clack and miss miss. Took the valve cover off and the rocker nut was backed out. Had a spare rocker arm (bought a set for a V8) so I put one of those on. Ran near two minutes and it backed out. Seems the little half ball the rocker socket rides on has little oiling cuts in it that cause it to rotate and un-screw the lock nut. These are not cheapo lock nuts either, good aircraft lock nuts, (Thankyou Boeing) but it still turned the nut out. Set it again and put a jam nut on top and life is good. Think I will just do this to all of them, I think as they wear in that things will be better, but just be aware that strange things can happen. If I had my choice I would use the pivots without the oiling cuts in them so they do not induce rotation in the ball. I did get to run it up a little today and it just pulls flat from 3,500 on up, only got to about 6,500 today, but it was pulling the same as it was at 5,000. Kind of fun. Larry

Curious the mechanical part of the lock-nut being nylon or base material ie solid crimped?

Nylon lock nuts are not to be used in heat areas nor used more than once, least that's how we did it on aircraft

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These are solid crimped aricraft locking nuts. They have plenty of torque to hold them in any normal conditions. Larry

"Polylocks" don't move.