Did you take a look at your rocker gear?
If your rocker arms/shafts are worn you wont get much oil flow to the pushrod side of the rocker arm. Then not much of a drip to the end of the rocker that acts on the valve.
I took my right hand rocker shaft off for a bit of an exploratory look at lifters etc.
I replaced two rocker arms and pushrods and i have reduced my ticking sound.

