The camshaft has a dual role in an internal combustion engine- to control fuel input and expel fumes.

Connected to the crankshaft through either the timing belt or chain, the camshaft comprises a number of radial cams, each of them either t exhaust valves or fluid input valves.

The camshaft is basically a  long rotating horizontal bar containing a series of rectangular cams, with the number of cams (or lobes as they are sometimes known) compatible with the number of cylinders in the engine.

Each lobe opens and closes the valves alternately on the engine cylinders. This continual movement allows fuel to enter the cylinders at the beginning of a cycle whilst enabling any combustion byproducts to be emitted at the end of the process.

As the camshaft spins, the cams alternately open and close the intake and exhaust valves in line with the motion of the pistons in an ongoing cycle. 

When the cycle begins, each piston starts its intake stroke first with the intake valve opening with the aid of its rocker arms, allowing the mixture of air and fuel in the intake runner to start flowing into the cylinder.

After the dosage has been completed in any cycle, the cam activates powerful springs programmed to return the valves to their closed position.

The camshaft is a focal point of the internal combustion process. As such, it is prone to a lot of wear and tear of the vehicle's lifespan, gradually reducing its efficiency.

Because it acts mainly behind the scenes, car owners and drivers were unaware of the issues that can arise with the camshaft, which can slowly creep up before the full extent of the problem emerges.

When considering a classic car for restoration, it is virtually impossible to recognize any physical defects with the camshaft. Even faults displayed during a test drive cannot be clearly defined as they are similar if not identical to the problems that can occur in the crankshaft or cylinder head.

One of the principal sources of premature camshaft failure is excessive end play which causes excessive wear in the distributor gear resulting in timing problems, witnessed by a significant drop in engine performance and fuel economy.  

The two principal permutations of camshafts to be found in an internal combustion engine are known as either the single overhead cam (SOHC) or the double overhead cam (DOHC).

The DOHC earns its title by being fitted by two cams per head. Inline engines come equipped with two cams, while V engines are fitted with four.

Double overhead cams are usually found on engines fitted with at least four valves per cylinder, as a single camshaft would be incapable of fitting sufficient cam lobes to activate all those valves, significantly increasing engine power.

The cams drive the crankshaft on internal combustion engines, with the power coming from either a belt or chain known as the timing belt or timing chain.

Timing belts are fragile objects and should be kept under scrutiny and changed precisely according to the manufacturer's specifications. If the timing belts breaks when the car is in motion, it will result in terminal engine damage, as the cam will cease to spin, causing the pistons to become locked inside the open valves, often causing the engine block to crack.

As their name suggests, timing chains are much sturdier than timing belts and rarely cause problems.

Fitted in cars produced during the Seventies and onwards, a few UK and European car manufacturers began to add timing chains during the Sixties. 

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