in aug issue of popular mech. pg. 118 tale of ticking tappets. use 1 qt. of marvel mystry oil for every 3 qts of eng oil, or seafoam ( these are anti-varnishing agents.) and run the engine and change the oil when its hot. if
that fails change the tappets. this may or may not help you buy another posting had simular noise problems & i hope he will see this. i will continue to look for his posting. goood luck. roll on and throttle-up.