I had the same problem on an old corolla with a 3k engine. I think I just put up with the ticking. Never did figure out that one. Maybe a worn cam? Or some other part of the valve train is worn?

I've got a rocker that wont quit ticking, I can adjust the valves all set to 14mm hot then run it & it still ticks. While running I can slip the feeler gauge in between the rocker & valve & it quiets up. I've adjusted them about 3 times tonight & no major change, its almost like its loosening up after adjusting but its still tight when I check it.

I suppose I could pull the rocker shaft & install another rocker & adjuster but I wonder why it does this. Any ideas anyone?
Thanks, evan