Jam nuts on adjustable /6 rockers????

Personally I would get a new rocker arm !!The screw is held in place by what is called an interference fit which means that the female end gets a tighter fit than the first few threads !Or,LockTite the rascal !!Just my .02

Well, we had a bunch of good, used rocker arms, so, we just took your advice and replaced it.

Thanks for your input!:D