[eschaider]

A rocker, roller or otherwise, will not remain centered on the valve stem. The reason is the roller or (rocker wear pad) traces out an arc that is determined by the distance from the center of the roller to the center of the pivot on the rocker shaft.

If you use the valve lift to establish the length of a chord describing the valve motion in the guide you can position the rocker to center the motion of the roller across the middle of the valve stem, favor the portion of the valve stem closest to the exhaust side of the head or favor the portion of the valve stem closest to the intake side of the head.

My personal preference, when building pushrod engines, is to center the motion of the roller across the middle of the valve stem. When you go to either of the exhaust or intake positioning models you place unnecessary side loading on the valve stem and the guide, resulting in premature wear of the guide.


Ed