What are the types of camshafts?

　　Single overhead camshaft (SOHC) engines were common in early automotive powerplants, when most cylinders were equipped with two valves per cylinder—a configuration that adequately met the engine’s operational needs. SOHC designs are relatively simple and cost-effective, delivering sufficient power for everyday driving, particularly strong low-end torque, good fuel economy, and straightforward maintenance.

　　Dual overhead camshafts (DOHC) have become widely adopted in the design of modern passenger cars as technology has advanced. In this configuration, the intake and exhaust valves are each controlled by a separate camshaft. The shorter drive train and fewer moving parts result in more precise and efficient valve actuation, which effectively increases both intake and exhaust flow. This enables the engine to deliver higher power output at high RPMs, thereby enhancing the vehicle’s overall performance.

　　A bottom-mounted camshaft is located within the crankcase. Although this layout is relatively conventional, it offers several advantages, including lower cost, high low-speed torque, compact dimensions, and excellent durability, making it commonly used in American-made cars and trucks. A mid-mounted camshaft is positioned at the top of the engine block; its introduction was aimed at mitigating some of the drawbacks of the bottom-mounted design and improving transmission efficiency. In contrast, an overhead camshaft is mounted on the cylinder head—a configuration now adopted by the vast majority of mass-produced vehicles. Its advantages are significant: it places the camshaft closer to the valves, reducing energy losses due to reciprocating motion, enabling faster valve opening and closing, allowing higher engine speeds, and delivering smoother operation.