CHAPTER 3 CONSTRUCTION OF AN INTERNAL COMBUSTION ENGINE

LEARNING OBJECTIVE: Identify the stationary and moving parts, the operating principles and their functions, and the basic testing procedures used in constructing an internal combustion engine. Describe the techniques used in reconditioning and adjusting valves and timing gear installation.

In the preceding chapter, you learned how the internal combustion engine operates. You also learned how the basic moving parts of an engine move in a timed relationship to one another during engine operation.

This chapter provides information on the many stationary and moving parts of an internal combustion engine. As a CM, you should be concerned with how these parts are made, what materials they are made of, and their relationship to one another for smooth and efficient operation of an internal combustion engine.

The information provided is to help you diagnose malfunctions of an engine and ways to correct them. Since the gasoline and diesel engines used in construction equipment of today are basically the same internally, the majority of information provided applies to both.

ENGINE CONSTRUCTION

LEARNING OBJECTIVE: Recognize operating principles and functions of stationary and moving parts within an internal combustion engine. Describe techniques used in valve reconditioning and timing gear installation.

Basic engine construction varies little, regardless of size and design of the engine. The intended use of an engine must be considered before the design and size can be determined.The temperature at which an engine operates determines what metals must be used in its construction.

To simplify the service parts and to simplify process and servicing procedures in the field, the present-day trend in engine construction and design is toward ENGINE FAMILIES. Typically, there are several 3-1 types of engines because of the many jobs to be done; however, the service and service parts problem can be simplified by designing engines so they are closely related in cylinder size, valve arrangement, and so forth. For example, the GM series 71 engines can be obtained in two-, three-, four-, and six-cylinder in-line models. GM V-type engines come in 6-, 8-, 12-, and 16-cylinder models. These engines are designed in such a way that many of the internal parts can be used on any of the models.

STATIONARY PARTS OF AN ENGINE

The stationary parts of an engine include the cylinder block and cylinders, the cylinder head or heads, and the exhaust and intake manifolds. These parts furnish the framework of the engine. All movable parts are attached to or fitted into this framework.

Engine Cylinder Block

The cylinder block is the basic frame of a liquid- cooled engine whether it be in-line, horizontally opposed, or V-type. The cylinder block (fig. 3-1) is a solid casting made of cast iron or aluminum that contains the crankcase, the cylinders, the coolant passages, the lubricating passages, and, in the case of flathead engines, the valves seats. the ports, and the guides.

The cylinder block is a one-piece casting usually made of an iron alloy that contains nickel and molybdenum. This is the best overall material for cylinder blocks. It provides excellent wearing qualities, low material and production cost, and it only changes dimensions minimally when heated. Another material that is used for cylinder blocks, although not extensively, is aluminum. Aluminum is used whenever weight is a consideration. It is not practical to use for the following reasons: