Use a magnetic-mount dial indicator touching the top of the rocker arm inline with the valve stem instead of a feeler gauge to check the clearance. If there is a dimpled rocker face the dial will reflect the true clearance instead of bridging over the feeler gauge blade.
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!