Once the valve guides get gunked up with varnish, the only sure fix is to pull the head, remove the valves, and clean the guides with a stiff-bristle brush and carb cleaner. Time-consuming, but effective! Anything short of that risks more problems!
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!