The position of the rocker's wheel is important. The wheel needs to roll across the top of the valve tip. At midlift the bottom of the roller wheel should be at the middle of the valve tip. Seen here, the wheel is at the first third of the valve tip at zero lift. Also, be sure there's at least .030-inch rocker to retainer clearance. At full lift, check that coil bind clearance is more than .060-inch.