A way to test the working of hyd lifters is to put downward pressure on the pushrod end of the rocker arm with the engine idling slowly.If the lifters are hydraulic and functioning properly after a few seconds the lifter will leak down and start to click loudly (louder?).When pressure is removed the lifter will quickly pump back up and quiet down.On v 8 chevys I use a hammer handle or similar non metallic block.
While we're on the subject, a noisy valve can be detected many times by laying your fingers on the rocker arm and the shock/click can be felt in contrast with the quiet ones.Even a minor click is detectable with a little practice.A very useful trick for me when hunting that one noisy assembly.
