Even a tiny bit of valve lash will do that. Of course, the more lash you have, the more noise it makes. I took off my rollers on my eddie heads with a Hyd. cam in it. The racket wasn't to bad, but loud enuff for me to be annouyed by it.
I re-re-re-adjusted the Passenger side, and only tightened to no lash, where I could not rock the rocker (?) by hand. Put on the cover, tightened it up, and it made lots of racket. Retightened all by 1/2 turn, and it helped, but now it's just noisy. May try the stamped rockers, but not sure if they can handle the lift and strength of the springs.