Hydraulic cams only run preload to keep the noise out. The more preload you run the better you chances of getting the lifter *pumped up* if you float the valves. If you plan on takeing it past 6500 rpm adjust them to zero lash. othe rthan the 1/4 turn of preload is fine.
As for you black and wet in that hole it would most likely be from oil going past the valve guide and seal. Since you lost the intake rocker the piston was trying to suck on that stroke yet had no air/fuel.
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