The preload of a hydro lifter could be as much as .060. If you soak them or pump them, you got that much more lift they will generate on the first few strokes. If your valve springs are maxed or you run a high lift cam and your piston to valve clearance is on the bleeding edge of contact, that .060 more that you didn't factor in could be an issue. Lifters usually bleed off in about 10-12 seconds (read that in a Johnson lifter white paper) so if you do install them pumped, the ones you crank down (on lobe) will eventually bleed off but the ones that are on the base circle are still .060 taller than spec and will lift that valve right up past its designed lift. Even if you set the preload, you could still force the valve off its seat .060 during set up. Just put em in dry and prelube, your gonna prelube anyway right?