What are we working on?
what size studs?
Lock nuts...like SBC self locking?
Longer pushrods and valves leave the rocker pivot ball higher up on the rocker stud. It weakens the vlve train at that point. How high are we talking?
Post a photo.
If the threads go completely through the lock nut your OK. But if it is to high on the stud, deflection at high RPM s could be a problem.
Post some pics.
Fact is stranger than Fiction