Abstract: Embodiments of a tappet are disclosed herein. The tappet has a front and a back, and the tappet includes a first stirrup and a second stirrup. The first stirrup has a first opening with a plurality of angular positions from 0° to 360°. The angular position of 90° and 270° correspond to the back and front of the tappet, respectively. The second stirrup has a second opening. The first and second openings are configured to carry a roller pin on which the roller is provided. The first stirrup includes a first region having a first depth below a first interior surface of the first stirrup. The first region extends from 150° to 210° around the first opening. The first region has a first end located at an angular position of between 180° and 270° and a second end located at an angular position of between 0° and 90°.

Abstract: A pump including a tappet biased into contact with a camshaft by a return spring is provided. The pump includes a torque transfer reduction interface mechanically interposed between the return spring and the tappet. The torque transfer reduction interface is configured to prevent spring wind-up generated by compressing and expanding the return spring from being transferred to the tappet to prevent the torque from causing the tappet to rotate relative to the camshaft about an axis extending perpendicular to the rotational axis of the camshaft.