Helpneeded! Valvetrain ticking in SBC

[TurboLark]

I'm trying to help a friend solve a rocker tick/clack coming from his SBC. I have adjusted valves a few times and it wont go away.
It is not a consistent noise. It will clack 2 or 3 times then stop, then do it again. I have noticed one strange thing though. the allen setscrew on 1 rocker adj nut is not running down as far as all the others. all these lock screws are 1/8-3/16" down into the adj nut. The one is just barely below flush with the top of the nut.
Could it be a valve sticking in the guide? any suggestions on what else to look for?
Thanks folks.

[Ron Sutton]

I "think" you have a lifter issue on the rocker that doesn't adjust the same. Can you pull the intake & look at that lifter?

[sam 74]

Probably a lifter, I had a roller lifter bridge break once and it made the a tick tick noise while the engine ran and it wasn't a constintant thing, what happened was a lifter lost its bridge and rotated on the cam, wiped the lobe and mushroomed the lifter and it was getting stuck from time to time and the spring was shooting it back down on the cam. It was a costly failure but not a total rebuild, I caught it in time.

[TurboLark]

Thanks guys. Guess we'll tear it down and see whats what. Good time for a cam swap while we are in there.