[RET_COP]

Getting the valve stem axis 90* or perpendicular to the center lines of the trunnion and roller tip centerline at half your net valve lift is partially correct. Because rocker arms are not geometrically correct the pushrod cup is not where it is suppose to be. Usually it is set to high in the rocker body, and when you get the valve side correct, the pushrod tip is slightly over arcs. Both side move in arcs and you want balance on both sides. Since you really cant get the balance you'll have to compromise. You will be better off getting a shorter pushrod than what wold be geometrically correct for the valve side so the push rod will not over arc ( losing cam information to the rocker arm). This will bring your pattern inboard a little and give you somewhat a better balance, hence the compromise. Rocker arm manufactures don't get it right for some reason. You can get surprisingly close to the outboard side of the valve tip without compromising your valvetrain. Smokey Yunick says .020 but that is too close for me. Lash caps my help to widen the tip but now you add height.