The bearings of an engine make up an important group of parts. Some bearings remain stationary in performing their functions, while others move. The primary function of bearings is to support rotating shafts and other moving parts, and to transmit loads from one engine part to another. To accomplish this function in a practical manner, bearings must (1) reduce the friction between the moving surfaces by separating them with a film of lubricant, and (2) carry away the heat produced by unavoidable friction. One group of stationary bearings serves to support the crankshaft. These bearings are

Figure 3-8. Upper and lower main bearing shells, bearing caps, and rear main bearing thrust washers.

generally called main bearings. (See fig. 3-8.) The main bearings consist of an upper bearing (shell) seated in the cylinder block main bearing support and a lower bearing (shell) seated in the main bearing cap. The thrust washers shown in figure 3-8 are used to take up the axial (back and forth) movement of the crankshaft. Additional information on bearings is given in chapter 4 of this rate training manual.