Pre-lubed Hydraulic Lifters

It'll work fine either way. I prefer to install them not pumped up, set lifter preload and then prime the engine. Either way will work. You won't magically "lose" the ability to set preload if you pump them up first. However, there is always the risk that an already pumped up lifter will not bleed down all the way and hang a valve open on initial start. That's why I prefer to assemble them not pumped up. All that said, I doubt very seriously I will ever use another hydraulic lifter on anything. So that solves that problem "for me".