In order to test the lifter, you simply push down on the exposed edge with a piece of wood (hammer handle works fine) and see if you an make it move. I think you are supposed to rotate the engine so that the cam is not exerting pressure on the valve via the lifter.

You'll know immediately if you have a bad lifter - you'll be able to force it to move up/down a little or a lot.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC