I have a big Extreme Energy Comp Cam in my 406 Pontiac motor. When I first got the car running the engine builder adjusted the valves like a Chevy because the Edelbrock aluminum heads. The cam & lifters made all sorts of racket.
I checked and he only went like a half a turn on the preload. I read the instructions from Comp and it clearly says one turn from zero lash. I went back and relashed everything to one full turn and the noise was gone and there was noticably more oil coming out of the pushrods.
I have not had a problem since. Made 346.1 horsepower at the rear wheels in my 69' Firebird. The engine is very stock beside the aluminum heads and cam.
Since then I have had to argue with several people about it. They keep saying the car will run better if I go back to 1/2 turn or less of preload. But I saw the oiling improvement with my own eye's and the noise disappeared. Its been running just fine for several years now since.
My cam specs are 240/246 duration @ .050" and .507"/.510" lift 110 LSA