So is this a Magnum? At any rate, hydraulic rollers generally need a bit more preload than flat tappets. So it's not surprising to see you going with more preload. Also, there's a right way and a wrong way to install factory style hydraulic roller lifters, although you didn't specify, I'll assume that's what you're using. The oil holes in the lifter bodies should all face the center of the engine. If they face the outside, they can bleed off some of the oil that needs to be retained, since that side is facing downhill. People argue over it, but I've witnessed it. It happens, stupid as it sounds.