Camshaft The camshaft carries the cams which operate the exhaust valves and the fuel pumps. As they operate once every revolution, the camshaft of a two stroke diesel engine operates at the same speed as that of the crankshaft. It is also very important that the fuel pump and exhaust valve operate at exactly the right time. So the cam is driven by the camshaft. Two methods are used: geared drive and a chain drive.

The chain drives are light, narrow in width and flexible The chain drives are light, narrow in width and flexible. However, they elongate in service, which will affect the camshaft timing and they have a life of about 15 years. Geared drives should last the life time of the engine. However the gear train is heavier and expensive. If the gear wheels are misaligned, shock loading will result, which can lead to broken teeth.

The camshaft is made in sections, each section spanning one or two cylinders. The individual cams are manufactured from steel, which are heat treated to give them a very hard surface, but retaining a tough interior. The cams are expanded into the camshaft in the correct position using either heat or hydraulic means. The couplings for joining the camshaft segments are also expanded hydraulically, allowing for adjustment and to facilitate the replacement of cam if necessary.

The camshaft runs in an under slung white metal lined bearing, lubricated by the diesel engine lubrication system. On engines with chain driven camshafts, as the chain elongates, the timing of fuel pumps and exhaust valve is retarded. When this retardation reaches a certain point, the camshaft must be retimed. This is done by expanding the coupling between camshaft and drive, using high pressure hydraulic oil and turning the camshaft to the correct position using a large spanner and chain block.