tapping valve question

i have an 89 b2200 with 120k miles. the engine is supposed to be self adjusting, but i don't think that really works to great. one of my valves is tapping and i tried changing my oil to a different weight.(went from 10w-30 to 10w-40). i also used some lucas oil treatment/stablizer. problem being that before, the valve would only tap when i ran it over 65 mph. now when i go above 25 mph it does it. i don't know what i can do besides rebuild/replace the head. anyone have any thoughts on what i could or should do? any input would help. thanks!

on a b2000 or b2200? they aren't self adjusting until like 93+:spit:

Wht do you care about the b22 when you have a SR20 to play with? I used to own a sentra se-r. And I made that FLIcker fast!