Camshafts

The camshaft, or cam for short, opens and closes the intake and exhaust valves, allowing the fresh air/fuel mixture to enter the cylinder for combustion, and the spent gases to flow out. Most production cams are iron castings that are supported on journals that rotate in bearings, with individual eccentric lobes to actuate each valve. A single cam can be located in the cylinder block, or one or two cams can be mounted on the cylinder head.

On Over Head Valve (OHV) engines, the block mounted cam actuates the valves via lifters that ride on the lobes, pushrods that transfer motion up to the cylinder head, and rocker arms that pivot on shafts or studs. Single Over Head Cam (SOHC) engines operate the valves using followers or pivoting rocker arms, while Double Over Head Cam (DOHC) engines, which have separate cams for the intake and exhaust valves, employ buckets between the cam and valves. The crankshaft drives the cam(s) using a timing chain and gears or timing belt and sprockets, at ½ crankshaft speed. The camshaft must be timed with the crankshaft so that valve opening and closing is perfectly synchronized with piston movement.

OE camshafts are designed for the vehicle’s factory configuration, and if you’ve modified your vehicle and/or have specific performance goals, your engine can produce much more power with an aftermarket performance camshaft. From increased mileage to towing, better street performance and a “lumpy” idle, to all out racing, we have the right grind for every application including hydraulic and solid, flat tappet and roller lifters. Along with the mods listed above, compression ratio, transmission type, differential gearing, and vehicle weight must be factored in when choosing a cam.

Specs will vary, but in general performance camshafts have higher lift to open the valves further, increasing airflow and power. Performance camshafts also typically have longer duration – the valves are open longer, which increases high RPM power. Longer duration is typically accompanied by increased overlap (when both intake and exhaust valves are open), which can enhance cylinder filling at high RPM, but can also result in less vacuum for power accessories at low RPM.

Lobe Separation Angle (LSA), the number of camshaft degrees between the centerlines of the intake and exhaust lobes, is another spec you’ll encounter. In general, a camshaft with a tighter (smaller) LSA makes more torque at lower RPM and increases cylinder pressure; valve overlap is increased, with less idle vacuum and a rougher idle. A wider (larger) LSA reduces maximum torque but the power band is widened and peak torque occurs at a higher RPM. There is more vacuum at idle and idle quality is improved. A cam can also be advanced or retarded during installation to alter the RPM where peak power is delivered.