Figure 3-7. - Engine crankcase.

The CRANKCASE (fig. 3-7) is that part of the cylinder block below the cylinders. It supports and encloses the crankshaft and provides a reservoir for lubricating oil. The lower part of the crankcase is the OIL PAN, which is bolted at the bottom. The oil pan is made of cast aluminum or pressed steel and holds the lubricating oil for the engine. Since the oil pan is the lowest part of the engine, it must be strong enough to withstand blows from flying stones and obstructions sticking up from the road surface.

The crankcase also has mounting brackets to support the entire engine on the vehicle frame. These brackets are either an integral part of the crankcase or are bolted to it in such a way that they support the engine at three or four points. These points are cushioned by rubber mounts that insulate the frame and body of the vehicle from engine vibration. This prevents damage to engine supports and the transmission.

The crankcase (fig. 3-8) is the basic foundation of all air-cooled engines. It is made as a one- or two-piece casting that supports the crankshaft, provides the mounting surface for the cylinders and the oil pump, and has the lubrication passages cast into it. It is made

Figure 3-8. - Aircooled crankcase.