hydraulic head slightly noiser once engine warm

hydraulic head slightly noiser once engine warm but quite when cold, anyone know why?
I'm using 10/40 semi synthetic.

Previous experience is oil starvation to which ever tappet is noisy. Excess carbon build up

its only slightly noiser over the whole cam, I just wondered if its the type of oil I'm using. Oil pressure light or buzzer not coming on when hot, pressure seems ok.

some moderator has relocated this thread in big block carbs, should be in big block injector seection.