TECH-LINE

CAMS 101

CAMS are integral with the success of the rocker arm; especially with MID-LIFT geometry. The BLUE circle is the CAM JOURNAL. The 118° (31') depicts the dashed YELLOW semi-circle beneath the WHITE BASE CIRCLE and CAM LOBE. This is the DURATION in CAM DEGREES, which is HALF your CRANK (and CAM CARD). The WHITE lines extending from the 165° are the GROSS Duration. Doubled, this is 330°. CAM LIFT is shown as .306". CLICK Illustration for DURATION.

CAM LOBE encircled by BLUE line which depicts the cam's ultimate limitation, as mentioned elsewhere; as well as TAPPET DIAMETER (not shown). All cams are ground with their nose taking maximum height from the inside diameter established by the cam bearing journals. All CAM LIFT is derived from REDUCING the BASE CIRCLE and blending the new ramps into the existing NOSE to keep this dimension as high as possible. This of course allows the tappet to sit lower in the block, but all it sees in operation is the degree of rise that the lobe ascends from the BASE CIRCLE. See next two illustrations for comparison.

NOTE: CAM LOBE, CAM BASE CIRCLE, CAM NOSE, ACCELERATION RAMP (also known as FLANKS) are illustrated. Double Click on any of these terms for more info under: DEFINITIONS.