Cam Shafts

A camshaft is a critical engine component in most internal combustion engines that uses egg-shaped lobes (cams) to precisely open and close the intake and exhaust valves. It is essential for the engines "breathing" process, ensuring the correct timing for the air-fuel mixture to enter the cylinders and for exhaust gases to exit.
Function and Operation
The primary function of a camshaft is to convert the engine
s rotational motion into the reciprocating (up-and-down) motion required to operate the valves.
• Valve Control: As the camshaft rotates, its pointed or egg-shaped lobes push against valve lifters or rocker arms, forcing the valves open. Valve springs then push the valves closed once the lobe has passed.
• Synchronization (Timing): The camshaft is connected to the crankshaft (which moves the pistons) via a timing belt, chain, or gears. This mechanical linkage ensures the valves open and close in perfect synchronization with the pistons movement, a process known as valve timing. In a four-stroke engine, the camshaft rotates once for every two rotations of the crankshaft.
• Engine Performance: The specific design of the cam lobes—including their duration (how long the valve stays open) and lift (how far the valve opens)—directly influences an engines power band, fuel efficiency, and emissions characteristics.
Location and Types
Camshafts are typically made from cast iron or steel and are located in different parts of the engine depending on the design.
• Overhead Valve (OHV): In older designs, the camshaft is located within the engine block, using long pushrods and rocker arms to actuate the valves in the cylinder head.
• Single Overhead Cam (SOHC): The camshaft is located in the cylinder head, directly above the valves (or using short rocker arms). SOHC engines use one camshaft per cylinder bank to operate both intake and exhaust valves.
• Dual Overhead Cam (DOHC): Found in most modern vehicles, this design uses two camshafts per cylinder bank, one specifically for the intake valves and the other for the exhaust valves. This allows for more precise valve control and improved high-RPM performance and efficiency.
Some modern engines incorporate variable valve timing (VVT) technology, which allows the engine to adjust the camshafts timing based on operating conditions to optimize performance across different speeds and loads.