Camshafts & Pulleys

The camshaft controls the opening and closing of the intake and exhaust valves. Its profile determines the valves’ movements and influences how the cylinders are filled.

A sport camshaft may have different lift, duration, and timing characteristics than the stock camshaft in order to alter the engine’s performance across certain revolutions ranges.

It can alter rated engine power, but the result depends on the cylinder head, intake, exhaust, compression ratio, and engine management system. A power gain is not guaranteed across the entire revolutions range.

Lift refers to the displacement dictated by the cam profile. A distinction must be made between lift measured at the cam and lift measured at the valve when the valve train uses a mechanical ratio.

Valve aperture duration indicates the angular interval during which a valve is considered open according to a defined measurement method. Values must be compared at equivalent measurement heights.

Valve overlap refers to the period during which the intake and exhaust valves are simultaneously open around top dead center between the exhaust and intake strokes.

An adjustable pulley allows the angular position of the camshaft relative to the crankshaft to be adjusted in order to achieve precise valve adjustment.

No. An adjustable pulley shifts the timing events within the engine cycle, but does not alter the shape of the cam profile or its intrinsic maximum lift.

You must consider the cubic capacity, cylinder head, valve train, and the desired revolutions range. The profile must also be compatible with the mechanical components and the engine’s tuning.

Not automatically. Pressure conditions and intake characteristics differ between engine types. You must check the manufacturer’s recommendations for turbocharged applications.

It depends on the cam profile and the timing system’s characteristics. Some mountings require specific springs to accommodate the anticipated loads and strokes.

A change in valve lift or engine timing can reduce the clearance between the valves and pistons. Mechanical contact can cause significant damage to the engine.

Timing may require a graduated shim disc, a dial indicator, and specialized tools. Follow the manufacturer’s specifications and procedure, then check the mechanical clearances.

Requirements depend on the camshaft design and the type of followers. Some mountings require a specific oiling and break-in procedure during the first start-up.

You must verify the engine part number, the mounting interface, the drive type, and the pulley sizes. Variable valve timing systems require special attention.