Had the too tight rocker issue on my Austin when I put together the new 4 bolt main 350 in it. Cam maker's spec was 1 to 1.5 turns after zero lash. But doing so made the engine idle fine, but all sorts of issues above idle rpm. I backed them off until the rattled, and then went to zero lash. Shut it off and added 1/4 turn preload and it ran perfect.