1. Cylinder: The cylinder or cylinder liner of an IC engine is fitted in the cylinder block, which is a
   single casted unit and is considered to be the main body of an engine. The block has cylinder liners. The piston reciprocates up and down from Top Dead Centre (TDC) to Bottom Dead Centre (BDC) to generate power.
   The cylinder liner and the cylinder block have to withstand very high pressure (about 70 bar)
   and temperature (about 700°C) during power stroke. The material used for the cylinder block
   must withstand such heat and also disperse it effectively. The cylinder block is well-designed
   with water passages to remove the excess heat and separate oil passages are provided for the
   circulation of lubricating oil. The top portion of the cylinder block is covered by the cylinder head. The crankcase is an integral part of the cylinder block which houses the crankshaft and the lower portion is dipped in an oil pan.
   Nowadays, cylinder liners are made of special alloy and internal portion is coated with material
   like titanium which provides mirror finish and can withstand the wear resistance. The upper end of the cylinder liner has a flange which fits well in the cylinder block. The exterior portion of the cylinder liner is exposed to water jacket for easy dispersion of heat.

2. Cylinder Head: The cylinder head is also singlecasted unit and bolted to the top portion of the cylinder block. The combustion chamber is a part of the cylinder head, where the combustion of gases takes place. The water passages are provided to remove the heat from the cylinder head. In latest engines, the cylinder head also houses the camshaft which has the inlet and exhaust valves with supportive valve mechanism. This provision is made to fix spark plug in SI engines and nozzle in CI engines. The lower portion of the cylinder head is well-machined
   to ensure there is no leakage of gases. Cylinder head gasket is usually cast as one piece and bolted to the top of the cylinder (engine block). Copper and asbestos gaskets are provided between the cylinder and cylinder‑head to obtain a gas‑tight joint. The charge enters the combustion chamber through the inlet valve connected to the inlet manifold, and the
   exhaust gases are removed through the exhaust valves connected to the exhaust manifold

3. Piston and Piston Rings: Piston is a cylindrical unit, used to compress the charge during compression stroke and to transmit the gas force to the connecting rod and then to the crankshaft during power stroke. The pistons of IC engines are usually made of aluminium alloy, which has high thermal conductivity and is light in weight. The material of piston must have the ability for higher heat transfer. The piston moves up and down (from TDC to BDC) and assists in completing the engine cycle.
   The piston rings are placed in the ring groove and provide sealing between the piston and the cylinder liner, thereby preventing the leakage of high pressure gases. These are made of special grade cast iron, which retains its elastic property even at very high temperature. The upper piston rings are called the compression rings and the lower piston rings are called the oiling or oil control rings.

4. Connecting Rod: It is usually manufactured by using drop-forged steel. It is made in the shape of ‘I’ so as to reduce its weight and to withstand strength. Its small end is connected to the piston with the help of gudgeon pin and the big end is connected to the crankpin with shell bearings. It has a passage for the transfer of lubricating oil from the big end bearing to the small end bearing (gudgeon pin). The major function of the connecting rod is to convert the reciprocating motion of piston to the rotary motion of the crankshaft.

5. Crank and Crankshaft: The crankshaft is called the backbone of an engine because it converts the reciprocating motion of piston into the rotary motion of the crankshaft. The crankshaft is a
   single casted unit and is made of drop-forged steel main journals which are placed and supported in the crank case. The main journal and connecting journals are machined to a smooth finish to reduce friction and shell bearings are used for smooth rotation of crankshaft. Front end of the crankshaft will transmit drive to the camshaft and also to the timing gear, whereas the flywheel is bolted to the flange at rear end of the crankshaft. Main journal of the crankshaft carries the oil passages to lubricate shell bearings.

6. Piston Pin or Gudgeon Pin. This unit connects the piston and small end of the connecting rod
   and passes through the piston . Circlips are fitted into recesses in the piston to prevent the gudgeon from touching the cylinder wall. The needle bearing or bronze bushing is press fitted into the connecting rod, due to this the gudgeon pin provides bearing for the oscillating small end of the connecting rod.

7. Inlet Valve: The major role of the inlet valve is to submit fresh charge in to the cylinder during the suction stroke. Opening and closing of the valve will control the admission of the charge into the petrol engine or air into diesel engine during suction stroke of an engine. The valve operations will be as per the valve timings. The inlet valve has a wider face or in latest engines two inlet valves are used to maintain volumetric efficiency of an engine.

7. Inlet Valve: The major role of the inlet valve is to submit fresh charge in to the cylinder during the suction stroke. Opening and closing of the valve will control the admission of the charge into the petrol engine or air into diesel engine during suction stroke of an engine. The valve operations will be as per the valve timings. The inlet valve has a wider face or in latest engines two inlet valves are used to maintain volumetric efficiency of an engine.

9. Valve Spring: The valve spring plays an important role to close the valve and also provides air tight compartment to seal the combustible gases during power stroke and also maintain the self-centering movement of the valve. Both ends of the vale spring are machined for
   smooth function and up and down movements of the valves.

10. Inlet Manifold: The fuel air mixture is carried from the carburettor to the cylinder through a separate pipe through inlet manifold in a carbureted engine. Whereas in compression ignition engines (diesel), the air is sucked through the induction manifold. In M.P.F.I the engine holds the throttle body on top of the manifold and the supply of air is monitored by the throttle body sensor.

11. Exhaust Manifold: It is a set of pipes and muffler, which is used to remove the exhaust gases from the exhaust ports. Engines oxygen sensors and catalic convertors are used to reduce sound and air pollution, respectively

12. Camshaft: The major function of the camshaft is to operate the intake and exhaust valves through the cam lobe, the gear drive transmits the power for the rotation of oil pump, therefore the oil pump sucks the oil from the oil sump and transits the same to the oil gallery. The camshaft is driven by crankshaft at half the speed of

13. Cam Lobe and Tappet: The cam lobe of the camshaft is placed directly above the bucket tappet, such that the lobe comes around it and pushes down the bucket tappet and the valve, thus opening the valve. In an overhead camshaft with rocker arm, the cam lobe comes under the valve lifter, and causes the rocker arm to rock or turn the lobe and pushes down the valve steam and it moves down to open. When the cam lobe passes the valve lifter the valve spring retains back to the original

14. Push Rod and Rocker Arm: The motion of the cam lobe pushes the valve lifter upwards. This movement pushes the push rod and the rocker turns the upward motion of the push rod to the downward movement of the valve stem resulting in opening of the valve.

15. Crank Case: The crank case is an integrated part of the cylinder block. The casing is provided to hold the crankshaft. The crankshaft is allowed to rotate freely and transmit the power to the flywheel

16. Water Pump and Water Jacket: The function of water pump is to draw water from the radiator and supply it to the water passages provided in the cylinder block and cylinder head with certain pressure. The circulation of coolant removes the excessive heat from an engine. This helps in maintaining the engine temperature and also the life of an engine

17. Radiator: The major function of the radiator is to radiate the heat from the coolants. It
    has two tanks located at the top and bottom. The upper tank is connected to the lower
    tank with the core through the passages for easy radiation of the heat. The radiator also Radiator stores the coolant

18. Flywheel: It is a wheel mounted on the crankshaft which stores the energy during the power stroke and transmits the energy to the transmission system, the clutch and then to the gear
    box

19. Governor: It is run by drive from the crankshaft. The function of the governor is to regulate the charge in case of petrol engine and amount of fuel in case of diesel engine to maintain the speed of the engine constant, when the load requirement varies. The components described above are commonly used for all types of IC engine. Here we are describing only a few components which are used in particular types of engines.

20. Carburettor: The major function of the carburetor is to supply carburised fuel as per
    speed and the engine load. In petrol engines the carburettor is mounted on the induction pipe or on the induction manifold. The quantity of fuel air mixture in appropriate ratio is controlled by the throttle valve and the movements of the throttle valve are connected to the accelerator.

21. Spark Plug: The function of the spark plug is to ignite the fuel air mixture after completion of the compression stroke in an engine. It is generally placed in the combustion chamber of the cylinder head. This is only used in petrol engine

22. Fuel Injection Pump: In case of diesel engine the diesel oil from the fuel tank is sucked by the fuel feed pump. The pump first sends the diesel oil to the fuel filter and then to the transfer pump. The transfer pump increase the pressure of the fuel.

23. Fuel Injector: The function of fuel injector is to break the fuel into fine spray (atomised condition) as it enters the combustion chamber of diesel engine.In case of an MPFI engine
    petrol is injected at the end of compression stroke as the fine spray of the fuel burns more efficiently in the combustion chamber giving better fuel efficiency with less air pollution.