Have you checked the cam lift on the noisy valve? It's possible you've got a worn out lobe that will never quiet down because the geometry is all wrong. One cam lobe on John's 261 had an extreme amount of wear so we had to replace the cam and lifters.
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!