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.