Use thin shims and tighten the side clearance up to .010, if not already.
It helps. Also running a larger induction hardened shaft is optimal setup here. Dan Dvorak sells the killer rocker shafts, over a 1/4 thick, core plugs are tiny in the ends. That's what I use and I never have a bleed off issue. Imo the shafts that come with almost all needle roller rockers are wrong size and hardness is all over the place. The rocker shouldnt be wiggling the slightest bit.
It should not just fall/slide onto the shaft like a hulahoop.
Jmo
