[Gaz64]

Any hydraulic camshaft, (flat tappet or roller), is designed to run with lifter preload, (after zero lash).

The camshaft base circle is ground differently than a solid camshaft.

Some guys might run their hydraulic preload as close to zero, as a safety margin against lifter pump-up. This only really occurs if the engine valve floats where insufficient valve spring pressure is used.

If you have adjustable valve train, and you want to run at just under zero lash, (eg: 1/8 turn past zero), then a periodic check doesn't hurt.

Otherwise, a correctly adjusted preload of 1/2 to 3/4 turn should be QUIET while the engine is running.

Some lifters are designed to be noisy regardless of adjustment. Rhoad lifters are the best example. Crane Hi-intensity are less noisy. The bleed off is designed to tame a little of the camshaft away at low speed, and give a smoother running engine when a wild cam is fitted. A little old school.

I have seen hydraulic cams fitted with hydraulic lifters that are converted to solid lifters. Those cams are NOISY, and have limited life.