OOPS! I got confused with the 51 he was talking about- - - -that doesn't rattle. It sounds like you've got one balky lifter if all of them don't get noisy at the same time. Try running a solvent-type oil additive for a while. We used to use Wynn's Friction Proofing for noisy lifters, but I haven't seen any of it in years. Marvel Mystery oil might be a pretty good substitute.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!