If you look at the basic working of engine, the valves play the most crucial part in tuning the performance of the engine. The valves are controlled by a cam shaft which in turn gets it’s drive from the teeth belt which is connected to crank shaft which holds the piston.

Unless the piston tends reach it’s top dead center, the valve should not be opened for which easy maintenance between the crank shaft and valves can be maintained with the help of cam shaft and teeth belt.

It maintains the co-ordination between the crank shaft and the valves so that valve timing retains at any cost, provided the teeth belt or chain provided don’t slip.

Apart from that, the teeth belt must have greater tensile strength and ability to withstand it’s structure without any sagging at higher temperatures. Which is why chain will be used in some engines.

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