The cylinder assembly completes the structural framework of an engine. As one of the main stationary parts of an engine, the cylinder assembly, along with various related working parts, serves as the area where combustion takes place. For purposes of our discussion, a cylinder assembly consists of the head, which covers the top of the cylinder, the cylinder liner, the gasket that forms a seal between the block (or frame) and the head, and the fasteners (usually studs with nuts) that hold the assembly together (fig. 3-9). The other engine parts shown in figure 3-9, many of which involve motion, are discussed later in this manual.

The design of the parts of the cylinder assembly varies considerably from one type of engine to another. Regardless of differences in design, however, the basic components of all cylinder assemblies function, along with related moving parts, to provide a gastight and liquid-tight space. Differences other than those in design can be found in various cylinder assemblies. For example, a gasket is necessary between the head

Figure 3-9.Principal stationary parts of a cylinder assembly.

and the block of most cylinder assemblies. However, such gaskets are not used on all engines. When a gasket is not a part of the assembly, the mating surfaces of the head and the block are accurately machined to form a seal between the two parts. Other differences are pointed out in the discussion that follows.