Im not sure about your year vehicle, but some of the early rover v8's had a problem with the camshaft moving back and forth causing a knocking sound at the front cover. there was a button you installed onto the front of the cam to stop this problem.

 

Yes...and not THAT early (from 1968 to 1992ish [from a lousy memory]).

The camshaft is not soundly locked in place. It is held a bit by the timing chain, a little pressure from the lifters and the interface with the distributor gear. The alloy and nylon timing chain Rover/LR used to use stretched easily and quickly, retarding the timing and allowing the camshaft to wander. That lead to all sorts of mischief. The engine would become a dog with retarded timing. The moving camshaft meant uneven cam wear, a moving camshaft gear, pieces the cam gear snapping off...and so on. It was a sad domino effect that would, at worst, destroy your timing cover.

Before engine builders and then LR moved to a decent timing chain, many people (including me) would try to keep the camshaft in place using what you are referring to, a cam thrust button, which is more commonly found with racers using with roller rocker engines.

This item in its Rover racing manifestation replaced the bolt holding the cam gear on with a threaded button with a low-friction rounded head whose length could be adjusted. We would dial it in to just barely touch the timing cover and keep the camshaft from moving in and out. Of course, that didn't help the chronic stretching chain issue. It was just dealing with one symptom. We tried a couple of buttons and then moved to vernier pre-stretched dual timing chains. That worked.

Considering the year of the vehicle here, I doubt a wandering camshaft could be the problem. A "ticking" sound is more often other issues.

James