I am in the process of adjusting my guide plates on my AFR 165 cc heads. They have 7/16 studs and I am using Scorpion 1.6 RRs. The part I am not sure about is does the pushrod run against the guide plate at all times? Or does it rotate back and forth from one side of the guide plate to the other? I adjusted to have the roller tip centered on the valve tip with equal clearance on both sides of the push rod. The problem is when I get one centered the other is off because the guide plate guides two valves.