Camshaft Profile This is...
This is the same camshaft mapped in the Valve Lift Plot illustration, but from a different perspective-from the end of the camshaft with all opening and closing points noted by colored dots. A roller lifter is in place on theexhaust lobe centerline.
As you can see in the valve lift curve plots, the intake centerline of the colored plot is installed 4 degrees advanced at a 106-degree centerline. The lobe separation angle is 110 degrees. The black curves are the same camshaft installed an additional 4 degrees advanced to achieve a 104-degree centerline. Advancing the intake lobe centerline starts overlap sooner and opens the intake more: It usually increases bottom-end power by moving the ideal operating rpm lower in the powerband. A rule of thumb is that advancing the intake centerline about 4 degrees from its original installed position will move the powerband to begin about 200 rpm sooner. Retarding it the same number of degrees will move the powerband up about 200 rpm. This can be useful for tuning the engine's powerband to a particular track. A camshaft that is installed "straight up" (neither advanced nor retarded) per the cam card that comes from the manufacturer is a good cam degreeing starting point.
Armed with these major terms and parameters in mind, contact your performance camshaft manufacturer for more detailed selection of a camshaft for your racing needs. The time you invest with them will be well spent.
Need To Know
Before you call a racing camshaft manufacturer, you should have these values in hand. The more you can flesh out these parameters, the better the camshaft will be matched to your performance racing requirements.
* Track type/size
* Camshaft restrictions/rules (i.e., flat tappet/lifter required)
* Engine size and number of cylinders
* Bore and stroke
* Compression ratio
* Connecting rod type/length
* Rocker arm ratio
* Carburetor size
* Intake manifold type
* Cylinder head brand/type, or flow data (best)
* Intake/exhaust valve size
* Transmission type
* Torque converter stall speed (if automatic)
* Rear axle ratio
* Rear tire size
* Fuel type and octane rating
* Car weight* RPM powerband operating range of engine