408 valve train noise

I have a 408 magnum, 12-1, E-85, .560 lift hydraulic roller, magnum R/T heads, all valve train from hughes. The problem is @ 2500 rpm it sounds like the lifters collapse, @ idle sounds like a sewing machine. I have tried adjusting the valves warm, cold, running, 0 preload, 1/4 preload/ 1/2 preload, 3/4 preload. No matter what I still have noise. I have noticed when I turn the engine over any lifter on high lobe will bleed off immediately, any rocker on off lobe will be loose (no preload). Is this typical of hydraulic cams?