LO 9-1 Identify the purpose and list the names of components associated with the cylinder head and valve train

1. What Is a Cylinder Head and Valve Train?

What Is a Cylinder Head and Valve Train?

The cylinder head is a metal casting forming a major engine component that is attached to the top of the cylinder block Figure 1. Cylinder heads, along with the cylinder head gasket, are needed to seal the combustion chamber so that the engine can develop compression and contain combustion pressure in each cylinder. Because compression and combustion pressures are much higher inside a diesel engine, cylinder heads are ruggedly constructed and require high clamping forces using more head bolts or specialized head bolts to secure the head to the block. As a major structural component of the engine, the cylinder head is an attachment point for other components critical to the operation of the engine. Numerous valve train and fuel injection components are attached or incorporated into the cylinder heads, which adds complexity to their construction and service. The cylinder head also contains drilled or cast passageways to fit injectors and enable the flow of coolant, fuel, and oil. Large ports for high volume intake and exhaust gas movement are also part of cylinder heads’ operating features Figure 2. Various sensors, such as the coolant temperature and cam position sensors, may be located in the head as well.

FIGURE 09-1: Major engine components. The cylinder head is a major engine casting that is bolted to the top of the cylinder block. The cylinder head gasket seals the block to the head.

FIGURE 09-2: Numerous components are supported by the cylinder head. Passageways for coolant, fuel, and oil are incorporated into the head casting.