PIN 7B0131 - Caterpillar

is one camshaft per side. The 3508B camshaft is supported by five bearings. Each camshaft is driven by the gears at the rear of the engine.As the camshaft turns, each lobe moves a lifter assembly. There are three lifter assemblies for each cylinder. Each outside lifter assembly moves a pushrod and two valves. The valves can be inlet valves or exhaust valves. The center lifter assembly moves a pushrod that operates the unit injector. The camshafts must be in time with the crankshaft. The relation of the camshaft lobes to the crankshaft position causes the valves and unit injectors in each cylinder to operate at the correct time.