TRANSMISSION AR 1391124 - Caterpillar

is one camshaft assembly per side. The 3508 camshaft is supported by five bearings. The 3512 camshaft is supported by seven bearings. The 3516 camshaft is supported by nine bearings. Each camshaft is driven by the rear gear group.As the camshaft turns, each lobe moves a lifter. There are three lifters for each cylinder. Each outside lifter moves a pushrod and two valves. The valves can be inlet valves or exhaust valves. The center lifter 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.