Page 158 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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142 Automobile mechanical and electrical systems

Figure 2.122 Oil drillings for the valve gear

Figure 2.123 Oil cooler for a racing car. (Source: www.prcracing.com Media)

connecting rod may be drilled along its entire length so that oil from the big-
end bearing is taken directly to the gudgeon pin (small end). The surplus then
splashes out to cool the underside of the piston and cylinder.
The camshaft operates at half crankshaft speed, but it still needs good
lubrication because of the high-pressure loads on the cams ( Fig. 2.122 ). It is
usual to supply pressurized oil to the camshaft bearings and splash or spray oil
on the cam lobes. On overhead camshaft engines, two systems are used. In the
simplest system the rotating cam lobes dip into a trough of oil. Another method
is to spray the cam lobes with oil. This is usually done by an oil pipe with small
holes in it alongside the camshaft. The small holes in the side of the pipe aim a
jet of oil at each rotating cam lobe. The surplus splashes over the valve assembly
and then falls back into the sump.
On cars where a chain drives the cam, a small tapping from the main oil gallery
sprays oil on the chain as it moves past, or the chain may simply dip in the
sump oil.
Some specialized vehicles use an oil cooler ( Fig. 2.123 ). The oil cooler commonly
used is an air radiator similar to an engine-cooling radiator, with tubes and fi ns
to transfer heat from the oil to the passing air stream. This cooler is fi tted next