I have set Dart Iron Heads 64cc with 180cc runners. In order get tips roller rocker some what centered over valves stems , put my push rods against intake runners going down thru head. I'm using guide plates also. You can just get piece paper between intake runner and push rod. Is this acceptable. I'm sure not happy with this. Something should move it could be ugly. Theirs not much material to cut out for clearance. I have standard pushrod with 1.52 rockers and .480 lift.