just noticed today car is making a tapping noise from the top of the engine , now when its idling its not tapping and when you rev it it taps, now its also not running as smooth as it was either, i had done headgasket a week ago and i only done oil change today as i though the oil would be a bit thin so i have done that and its still tapping a bit and idles a bit rough for a second then smooth then rought again. i took off rocker cover and it all looks and feels tight , what could it be??
anyone else had something similar