New lifters won't pump up

[nathan 73 dart]

I recently took my dart out to the drags and lost a couple of pushrods in my 440. Turns out a couple of lifters were stickking so I bought a new set of Lunatti's from Summitt. They seem to be of good quality. I soaked the lifters overnight then set up the lifters with 1/2 turn of preload past 0 lash. I ran the motor for about 5 minutes and their seemed to be a lot of clatter from the rocckers so I pulled the valve cover and a couple of lifters seemed a little soft. Should'nt they be pumped up after 5 minutes any advice would be helpful.

 

[bOb shingler]

try a heavier weight oil

 

[PFogel]

Doesn't sound good. How much oil pressure does it have? Even a minimum of 20-lbs will pump them up. Look and see if it is eating up a cam lobe - just look at the bottom of the lifter. I have had much success preloading just 1/4 turn. It sounds like your engine is consuming itself.
Pat