The main difference between a Harley-Davidson V-twin engine with dual overhead camshafts (DOHC) and one with single overhead camshaft (SOHC) lies in the design and operation of the camshafts.
Single Overhead Camshaft (SOHC): In an SOHC configuration, each cylinder of the V-twin engine has a single camshaft located in the cylinder head. This camshaft operates both the intake and exhaust valves for that cylinder through various mechanisms like rocker arms or pushrods. The camshaft is positioned above the combustion chamber and is driven by the engine's timing chain or belt.
Dual Overhead Camshafts (DOHC): With a DOHC configuration, there are two camshafts per cylinder head—one for the intake valves and another for the exhaust valves. The camshafts are positioned above the combustion chamber and are directly connected to the valves, usually through bucket tappets or shim-under-bucket designs. This configuration allows for more precise valve control and generally allows for higher RPM capabilities.
The choice between SOHC and DOHC depends on various factors, including the engine's intended use, power requirements, and design philosophy. Here are a few key considerations:
Complexity and Weight: SOHC engines are typically simpler and lighter due to having fewer camshafts and associated components. DOHC engines require additional camshafts, valve mechanisms, and often have more valves per cylinder, which can add complexity and weight.
Valve Control: DOHC engines generally provide more precise valve control because each camshaft independently operates the intake and exhaust valves. This can result in better performance at higher RPM ranges and potentially increased power output.
Cost and Manufacturing: SOHC engines are generally less expensive to manufacture due to their simpler design, requiring fewer components and machining operations. DOHC engines, with their increased complexity, may incur higher production costs.
It's important to note that while DOHC configurations are more commonly found in high-performance motorcycles and modern sport bikes, Harley-Davidson traditionally utilizes a design with a single camshaft per cylinder head (SOHC) in its V-twin engines. However, engine designs can vary over time, and it's always best to consult specific model specifications or reach out to Harley-Davidson for the most accurate and up-to-date information regarding their engine configurations.