Lube up the lifter with assembly lube and stick it in the hole. It should, just by gravity, fall out the bottom of the lifter bore. I put my finger below the bore, beneath the base circle of the cam. Then I let the lifter "fall" onto my finger. Push it back up, spin it and do it again. Do this several times and if it floats freely, you are fine. If you feel any little burr or something that catches the lifter that is bad.Not to hijack the thread but need schooling on bushing of the lifter bores. What tolerance should be there etc. I guess I need to tear my engine apart and recheck everything as I had a shop do everything. I don't want any problems. Also what break in grease or not do I use for cam and rockers if any. I have always in the past put grease on the cam shift then drain after break in. Now back to the thread I see what dvw is saying and I agree those valves didn't just happen talk to the shop for some kind of fix.
If the cam is installed and you don't feel like removing it, I guess you could just let the lifter drop to the base circle of the cam and test them that way.
Bottom line is flat tappet cam lifters must spin. The spinning action helps create the oil film that the lifter rides on. The cam lobe is actually tapered to cause this. If a lifter doesn't spin, you'll have trouble in a hurry. Startup also requires zinc in the oil. The zinc gets embedded in the metal of the cam and creates a type of lubrication. But more zinc is not better. Go for 1500 to 2000 PPM of zinc. Too much zinc makes the oil acidic which is bad too. Any of the good break in oils should be fine.