Cylinder head

DOHC-Zylinderkopf-Schnitt

Head D15A3

Malossi 70cc Morini cylinder head

Suzuki-GS550-DOHC

Cylinder-head

Cylinder Head

The cylinder head is a crucial component of an internal combustion engine. It sits atop the cylinder block, closing the top of the cylinders to form the combustion chamber. This part is vital for controlling airflow in and out of the cylinders and housing components such as the spark plugs, valves, and fuel injectors in gasoline and diesel engines, respectively.

Design and Function

The design of the cylinder head is complex and varies significantly depending on the type of engine (e.g., gasoline or diesel), its intended use (e.g., passenger car, truck, racing), and its manufacturer. However, common functions across all types include housing the intake and exhaust valves, passages for the fuel-air mixture, and channels for engine coolant to help dissipate heat.

Valve Configuration

The arrangement of valves in a cylinder head is critical for the engine's performance, efficiency, and emissions. The most common configurations are:

• OHV (Overhead Valve): The camshaft is located in the cylinder block, and valves are operated through lifters, pushrods, and rocker arms.
• OHC (Overhead Camshaft): The camshaft is located in the cylinder head itself, allowing for more direct actuation of the valves. This configuration can be further divided into SOHC (Single Overhead Camshaft) and DOHC (Double Overhead Camshaft), depending on the number of camshafts used.

Material

Cylinder heads can be made from various materials, including aluminum alloys and cast iron. Aluminum alloys are lighter and offer better heat dissipation, making them a popular choice for modern engines. Cast iron heads are heavier but provide excellent durability and are less expensive to manufacture.

Cooling and Heat Dissipation

The cylinder head contains passages for coolant to flow through, removing excess heat from the combustion process. This cooling system is critical to prevent engine overheating and to ensure optimal operating temperatures. In air-cooled engines, the cylinder head features fins that increase surface area for heat dissipation directly into the air.

Common Issues

Cylinder heads can suffer from several issues, including:

• Cracking: Overheating can cause the cylinder head to crack, leading to coolant leaks, loss of compression, or engine failure.
• Warping: Similar to cracking, overheating can also cause the cylinder head to warp, affecting the seal between the head and the block.
• Valve problems: Worn or damaged valves can lead to loss of power, increased emissions, and engine misfires.

Maintenance and Repair

Regular maintenance, including coolant system checks and timely oil changes, can help prevent cylinder head problems. In the event of damage, cylinder head repair may involve resurfacing the head, replacing valves, or in severe cases, replacing the entire head.