4842 Automotive Engines-Ghost: Four stroke engine

A four stroke engine works by using four cycles: Intake, Compression, Power and Exhaust

Intake: On intake the piston moves from T.D.C(Top Dead Center) to B.D.C to reduce the pressure in the cylinder a mixture of fuel and air is pushed in by the intake valve opening then the intake valve closes completing this stage of the intake stage

Compression: With both the intake and exhaust valves closed in this stage the piston moves back up applying compression to the fuel air mixture, this completes the compression stage

Power: When the piston is close to the T.D.C(Top Dead Center) the compressed mixture of fuel and air is ignited by the spark plug, the resulting pressure from the compression forces the piston back down to the B.D.C(Bottom Dead Center) with tremendous force, this completes the power stage

Exhaust: On the exhaust stroke the piston again returns to T.D.C only this time the exhaust valve is opened to let the spent air and fuel mixture through to the exhaust system, this completes the four stroke engine cycle

Nikolaus august otto invented the four stroke engine in 1864, the engine was perfected in 1876 however when the first four stroke was built(http://library.thinkquest.org/C006011/english/sites/ottomotor.php3?v=2 , http://inventors.about.com/library/inventors/blotto.htm ).

The purpose of the crankshaft is to turn up and down motion of the pistons to a rotating motion, the bottom of the pistons are connected to the crankshaft with main bearings.

The purpose of the camshaft is to open and close the intake and exhaust valves in the engine.
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The purpose of the head gasket is to seal the cylinder to ensure maximum compression and avoid the leakage of coolant and/or oil from getting into the pistons

The purpose of the piston is to transfer the force of expanding compressed gas in the cylinder down to the crank shaft via the piston/connecting rod, with some engines the piston also acts as a valve opening and closing ports in the cylinder wall.
The piston ring is an open-ended ring that fits in the grove of a piston in a combustion engine, its purpose is to seal the combustion chamber, it also supports heat transfer from the piston to the cylinder wall, lastly it also regulate engine oil consumption.

The purpose of the cambelt(also known as the timing belt) is to control the timing of the engines valves, it is run around the camshaft gears and the crank pully gear, the teeth on the belt turn the camshafts in-sync with the crankshaft

The purpose of the fly wheel is to steady the rotation of the shaft when we have fluctuating torque put onto the engine from its power source, it uses inertia momentum for rotational energy.

The purpose of the valve keepers is to hold the valve washer in place while connected in to the groves of the valve stem.