I had a very reputable engine builder do the cyl head, but when I got the car back, the noise was unacceptable. They took it back and measured the valve clearances. All were correct bar one intake valve with .007 rather than 0.004”. Very embarrassing. Bad measurement, or bad calculation. They sorted this, but the cyl head is not as quiet as it should be. The valve guides did not need replacement as the called them good.what else could cause the noise? Or what other parts should they have replaced?
I had another shop do a head many yrs ago, and that is still so sweet, and Well balanced. It is a 420G with that large air plenum, so easy to see any vibrations. That shop shut down after the owner got too old.
I dont know what parts he replaced.