Originally Posted by cobalt327
After thinking about this and doodling on paper, I believe the flaw in my thinking is that because the pushrod cup and the rocker roller are not on the same "plane" (maybe not the right term, but hopefully it will still be understandable) w/one another, the roller will describe the motion as depicted in the diagram, and Bogie's description. If the two points were perpendicular(?) to the rocker stud, or if the roller were lower than the p-rod cup, my theory might hold true. But because the roller is positioned above the p-rod cup, the movement is as Comp/Bogie said.
I do believe that if the lift were high enough that there's a possibility that an 'ordinary' rocker arm might go towards the exhaust side per Comp/Bogie, then at some point actually reverse and move back towards the intake side again. But in practice I doubt this will occur until lifts were enormous and even then the design of the rocker might be able to counter that effect.
Imagine standing with your shoulder in plane with the top of the book case, and you swing your arm (straightened) around to slap the top- your action is completely perpendicular to the top of the case. If you lower yourself your action is actually slightly askew to the case and pushing it outward, also the corner of the case will touch further out on your finger tips. If you raise yourself above so your waist is inline with the case and swing again your action is now askew and slightly towards yourself, you again will meet the corner further on out on your finger tips.
Clear as mud right?