In large engines of early design, support for the main bearings was provided by a bedplate. The
bedplate was bolted to the crankcase and an oil pan was bolted to the bedplate. In some large engines of more
modern design, the support for main bearings is provided by a part called the base. Figure 5-3 illustrates such a
base (which is used with the block shown in Figure 5-1). This type of base serves as a combination bedplate
and oil pan. This base requires the engine block to complete the frame for the main engine bearings.