LO 9-1 Identify the purpose and list the names of components associated with the cylinder head and valve train
| Site: | CDX Learning Systems |
| Course: | DE Section 2-1: Engine Blocks and Cylinder Heads |
| Book: | LO 9-1 Identify the purpose and list the names of components associated with the cylinder head and valve train |
| Printed by: | Guest user |
| Date: | Thursday, 5 November 2026, 7:49 PM |
1. What Is a Cylinder Head and Valve Train?
LO 9-01: Identify the purpose and list the names of components associated with the 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. |
©2026 - CDX |
1.1. What Is a Cylinder Head and Valve Train?
LO 9-01: Identify the purpose and list the names of components associated with the cylinder head and valve train. |
|
Integral to the cylinder head is the valve train, which is the engine system responsible for synchronizing piston and crankshaft position with the opening and closing of intake and exhaust valves. The valve train controls the flow of intake air and exhaust gases passing through the engine cylinders and compression release-type engine brakes used by many heavy-duty (HD) diesels Figure 3. To regulate valve operation and engine breathing, a rotating camshaft with a lobe for each of the intake and exhaust valves controls valve lift, valve closing, and the duration of valve opening. Camshafts are located either in the block or the cylinder head. Valve train components not only include camshafts but also gear or belt drive systems to synchronize the rotation of the camshaft to the crankshaft. Other essential components of the valve train in any engine include intake and exhaust valves, valve guides and seats for valves, valve springs, rocker levers, valve bridges, pushrods, camshaft followers, and valve lifters. Information in this chapter adds more detail to this outline of the cylinder head and valve train components. As a major component of the diesel engine that regularly encounters various types of failure and is routinely serviced, technicians should be familiar with construction operation and service of the cylinder head and valve train components. Information on this topic will help technicians acquire skills related to correctly servicing, maintaining, and diagnosing problems with cylinder head and valve train components. |
FIGURE 09-3: The smaller fifth valve in this MBE 4000 engine is for the compression release brake. |
©2026 - CDX |