Understanding Cam Specs

UNDERSTANDING A CAM CARD
At the right, we have the information from a COMP Cams cam card for a Magnum 280H Mopar big-block hydraulic performance cam. The cam card provides the critical specs of the cam, and other useful information. The first section provides general information such as the part number and application, as well as other descriptive characteristics, such as the single-bolt nose for this particular cam. The second section give the basic lift and duration specs. The lift is calculated on the factory 1.5:1 rocker ratio. Note that the duration is listed along with the tappet rise at which it is rated. The next section provides the actual intake and exhaust lobe opening and closing points. As with duration, the tappet rise these points are derived at is also listed (0.006 inch in this case). These points can be used to check the cam's phasing or installed centerline when degreeing-in the cam. The next section lists the duration @ 0.050 inch, the lobe lift, and the lobe separation angle. These numbers can be used to compare other cams listing these same standardized specs. Finally, we have the valvespring recommendation. Matching the valvespring to the cam's requirement is critical to getting the most from a given combination.