Hi Guys,
I still haven't really figured out this problem I have with my hydraulic lifters. The engine is a fresh rebuil, was broken in correctly and has about 5000 mls on it. Its an old 350 SB though, from before 1986 (no electronic stuff).

My lifters always seem solid and don't bleed down anymore after about 300 mls of driving. Then I have to take them out, empty them, clean them, put them back in again, set all the valves and off it goes like a rocket, drives absolutely fine for about 300 mls, then I have the same problem. The lifters act as if they were solid, and if I try giving them some preload, that will open my valves before the lifters compress. (I already have double valve-springs) This happens equally on all 8 cylinders. A friend of mine said I might be running too good oil. I have 10W40 High-Grade Liqui-Moly with MoS2 additiv. Damn expensive, but said to be very good. My friend said I should run thicker oil, something like 10W30, because the thin stuff runs through the engine without staying on anything. Can that be true? Will that affect my lifters? The lifters are almost new and show virtually no signs of wear, they don't bind mechanically, it's just the oil pressure in the lower compartment that keeps them up all the time.
The lifters do compress slightly when the valve is fully open and the engine is running, but not as much as they should do and the preload keeps the valves very slightly open at ALL times, which is not a good thing.
Who can help me? Thanks a lot,
MadMax