Hughes "retro fit" lifter not pumping up!

The above comment has me scratching my head..... I have had very hydraulics not bleed down overnight' especially 'back in the old days', it seemed to never happen. At least not that I have ever detected....and my hearing was quite good 'back in the old days' LOL

i can't get any set of flat tappet lifters to hold over night , even without rocker arm load . some will hold pressure , never the same bore . get i got to go one good one at a time . i've got a bench full of lifters , here goes day by day . pulled the plugs so it rotates easy with the start , turn it over with the starter until i get pressure up lifters , then a few more to keep it there . and come back a day later and check them for piston plunge , keep the ones that hold . and replace the rest . start it again . anyone know a better way ? please tell me . and no the customer wants a quite motor the start without any rattles . even after a month or more of setting . its just a clean driver , i want the same thing for him . it just a 340 la block and heads , nothing trick , just well dome .

What oil weight is being used? Lighter oils seem to be more of a problem.

Sounds like you need to set up a test stand and apply about 1.5 times the open spring pressure to each lifter after manually pumping up. Perhaps come up with a technique with a dial indicator to see how much they bleed down in an hour, or some other fixed time frame.