Check the underside of the rocker arm tips where they contact the valve stem. Quite often there is a step worn into the contact face that prevents a good valve adjustment being made. If the rockers are smooth, redo the static valve adjustment procedure. Continuing to tighten the adjusters until the noise goes away is risky business- - - -as the engine warms up the pushrod length grows due to heat and the lifter won't be able to compensate for the extra length if the plunger is adjusted close to bottoming out.
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!