From OUTLAW
Hydraulic lifters-
If your friend has an engine that , when started now, ticks VERY SLIGHTLY, and in 30 minutes of running time does not clear up, and the noise definitely comes from lifters, not just a slight exhaust leak- (makes similar sound), he probably has lifters that have varnish in them. If this same engine ran good last year with no noise, chances are a small dose of Rislone or similar brand name product ( used to clean lifters) combined with a fresh oil change, will free up the offending plunger (s) .( Remember, I said slight lifter noise.)
Noisy lifters results from many problems: dirty oil/ wrong viscosity oil/ short trip where oil is not warmed up/ improper adjustment/ soft cams/ rocker arm alignment problems/ high rpm abuse/ using old lifters on a new cam/ improper break in of new cam /cam out of time where valves contact pistons and push rods bend/ and like your friend says, lifter bleed down during storage..
You are right- excessive noise in the valve train leads to damage.
