TM 5-3805-255-14
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ENGINE CONTINUED
Camshaft
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The camshaft is located in the crankcase on the left-hand side of the engine, and is held to the crankcase by a hub
which takes thrust. The camshaft is supported at intervals along its length by seven bushings. These bushings are
removable and are furnished for service reamed to size. Bushings are a press fit in the crankcase.
The camshaft's main function is operating the intake and exhaust valve mechanism by action of its lobes upon
tappets to push rods during rotation.
It is important to notice that the camshaft gear has twice as many teeth as the crankshaft gear which drives it. The
camshaft, therefore, rotates at one-half of crankshaft speed due to requirement to open and close valves to each
cylinder once for every two revolutions of crankshaft.
The camshaft bearings are pressure-lubricated and have oil holes drilled in them. When bushings are installed, oil
holes must align with ones drilled in crankcase. Slots in two of the journals permit lubricating oil to travel to rocker
arm assemblies.
Figure 3. Camshaft Components.
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