i got this from an engine building forum,
I have seen several threads promoting priming hydraulic lifters. The lifters are a two part design fitting into each other. There is a small spring inside pushing them apart or making them longer. Basically, they allow oil in to fill whatever gap is inside and the lifter will automatically grow in length by oil pressure taking up any valve lash. The check valve prevents oil from leaving and allows it to hold the position.
I have found that the ball checks in these lifters seal VERY well and the lifters don't collapse smaller very easily without pushing on the check ball which requires removal from the rocker
Why am I bringing this up? By priming the new lifter you essentially end up installing the lifter at it's full length. While rotating the engine for assembly, oil priming etc the lifter is allowing the valve to open significantly more than it would normally, running a risk of the spring retainer smashing the valve stem oil seal or possibly coil bind and perhaps even valve to piston interference (I haven't checked that though) Bottom line, the valve can't rest on it's seat.
Yes, they will eventually adjust themselves but it takes time. It only takes one revolution to do damage if they are too long.
My suggestion is to bleed (not prime) the lifter until the rocker arm can be moved slightly when the rocker is on the base circle of the cam. The lifter can be bled easily (before installing) by squeezing the lifter, holding upside down and pushing a paper clip against the check ball allowing the oil to come out. Done this way, the lifter will fill from loose to tight and not be forced to go from tight to loose. The lifter ticking for a minute or two won't hurt it and my opinion is that it's much safer.
