A schematic diagram of an Engine function and Engine parts names and pictures is shown below. However, each part and its functions are discussed briefly afterwards.

Engine Diagram

Component parts of Internal Combustion Engines

Cylinder Block

Cylinder Block

The cylinders of a multi-cylinder engine are cast as a whole and it is called cylinder block. The cylinder block is the main supporting structure of an engine. Cylinder block is mounted with cylinder head at top and crankcase at the bottom. Both cylinder head and crankcase are attached to the cylinder block with the help of nuts and bolts. Cylinder head consists of systems for air, fuel injection and spark plug (in case of SI engines) (explained below). Crankcase gives housing to crank and acts as a sump for lubricating oil. At every joint for e.g. in between cylinder block and cylinder head a gasket is placed. A gasket provides a leak free joint and allows heat conduction between different parts. Cooling jackets are provided in cylinder head, cylinder block and crankcase assembly. The inner surface of cylinder block, which is machined to a cylindrical shape is called bore or face.


As the name suggests the cylinder is cylindrical in shape. This the actual place where fuel burning happens and piston reciprocates. A cylinder is machined with a very high surface finish. It is case hardened, to obtain a hard scratch free surface.



A piston is a cylindrical component, which fits inside the cylinder and forms a movable boundary. A piston moves smoothly inside cylinder, with the help of proper lubrication. A piston makes almost airtight contact with the cylinder walls, with the help of piston rings (explained below). Piston is the first link in transmitting the gas force into crankshaft.

Combustion chamber

A combustion chamber is an enclosure formed by cylinder walls, cylinder head and piston head. It is a place where the actual combustion of fuel takes place.

Intake manifold

Intake and Exhaust Manifold

Intake manifold is the pipe which brings air or air-fuel mixture into the combustion chamber for combustion. It is connected to intake valves (explained below).

Exhaust manifold

Exhaust manifold is a pipe with takes out exhaust gases from the combustion chamber after combustion. It is connected to exhaust valves (explained below).

Intake and Exhaust valves

Inlet and exhaust valves are used to control the regulate charge coming to engine for burning and exhaust gases going out from the cylinder respectively. They are provided either on cylinder head or on cylinder walls. They are commonly mushroom shaped poppet type.

Spark plug

Spark plug

A spark plug is a device used to initiate combustion with the help of a spark in SI (spark ignition) engines. Spark plug derives its power either from a battery or magneto.

Connecting Rod

Connecting Rod

A connecting rod transfers reciprocatory motion from piston head to crank shaft, where it gets converted into rotary motion. Connecting rod has two ends small end and big end. Small end is connected to piston head with the help of gudgeon pin (explained below) and big end is connected with crankshaft with the help of crank-pin.



A Crankshaft converts reciprocating motion of the piston to rotary motion with the help of connecting rod. Crankshaft has provisions for static and dynamic balancing.

Piston rings

Piston Rings

Piston rings are fitted in piston to provide leak free contact between piston and cylinder wall. However, they permit a small amount of lubricant pass through to provide lubrication for smooth running. They are designed to bear high temperature and thrust.

Gudgeon pin

It connects small end of connecting rod and piston.



The camshaft controls the operation and timing of inlet and exhaust valves with the help of a mechanism consisting of timing gears. It also provides drive to ignition system.


These are integral part of camshafts to control inlet and exhaust valve timings.


The torque provided by the engine is not uniform and is fluctuating in nature, to cater this problem a flywheel is used. It stores torque when its value is high and release it when its value is low in a cycle of operation. It acts as a torque buffer.

Enjoyed reading Engine parts, also read applications of different types of engines

Image credits

Camshaft, Piston Rings

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