Home - Automobile - Components of internal combustion engine

Components of internal combustion engine

Reading and knowing how an internal combustion engine works is okay but not knowing its components makes it useless. The coupled component of a vehicle’s engine makes the magic works beneath the bonnet, well it looks like magic to some people.

An automobile engine is built with different components with different sizes having their various intended functions. This article is targeted on the common type of automobile engine “internal combustion engine”.

The modern version of the engine parts combines both mechanical and electrical components. Read some important articles on internal combustion engine …

components of internal combustion engine

Car engines are contained around a sealed, resilient metal cylinder. It contains as many as sixteen cylinders but most modern vehicles have between four and eight cylinders. Reading my previous articles, you will understand the function of the cylinder is to open and close at a timing, allowing fuel and air to enter the chamber for combustion and releases the exhaust gases. well, that’s already explained content. Check it out in the above link!

In this article, I have distributed a list of essential parts of internal combustion engine and their diagram and their functions.

Components of Internal Combustion Engine:

Below are the common parts of an internal combustion engine:

1. Cylinder:

These automobile engine parts are located in the engine block also known as the cylinder block. It contains a liner or sleeves around it. This liner is worn out when subjected to work and can be easily replaced. The cylinders have part or space for the piston to move upward and downward, making the combustion to take place.

Cylinders are characterized by their bore and stroke. The bore is the inner diameter and the stroke is the effective length along the piston reciprocates i.e. the movement of the piston from the TDC to the BDC, they are the uppermost and the lowermost point of the stroke.

The cylinder block also contains some hollow space around and in between the individual cylinders, these hollow parts is known as jackets. It allows coolant to enters and circulates to enables effective heat dissipation in the case of liquid-cooled engines.

2. Piston:

The piston is a cylindrical part that moves upward and downward in the cylinder, allowing the complete combustion cycle to take place (intake, compression, combustion, exhaust) check out how this process works below.

The diameter of the piston is a bit less than the bore of the cylinder to avoid quick wear of the piston surface. There are three rings known as piston rings fitted in the circular recesses on the piston surfaces. These rings are made of aluminium, having direct contact with the cylinder liner, thus preventing piston wear.

The two first rings are compression rings, it is chamfered on the outer part, helping to cause the blowby effect (prevention of waste gases inside the combustion chamber from entering into the crankcase.) the third ring is known as the oil ring, it prevents oil from entering the combustion chamber and ensure proper distribution of oil along the cylinder walls.

3. Crankshaft:

These engine parts helps to converts the sliding motion from the piston into rotary motion via the connecting rod. It is located below the cylinder block inside a casing called the crankcase. The crankshaft has projections bent and offset from the shaft axis. In a multi-cylinder engine, each cylinder is provided with his own crankpin, provided to attach the piston by the connecting rod.

A part of the crankshaft named crankpin journal bearing is known as a big end, having a sliding bearing. Another part of it called counterbalance weights. It is provided to counter the tensional vibrations experienced by the crankshaft because of the reciprocating unbalance of the moving piston during the combustion process. the crank balance is either bolted to the crank body or form an integral part.

Crankshafts are either produced in parts or as a single piece. The single-piece design is more preferable because it leaves no space for vibration and offers a better fibre flow and good stress-bearing capabilities.

Finally, crankshafts are typically produced from steel by roll forging or ductile steel through casting. whilst single piece crankshafts are made from heat threatened carbon steels. Some other steels like vanadium micro-alloyed steels are also used due to the higher strength it can offer without heat treatment.

4. Connecting rod:

These engine parts are provided to connect the piston to the crankshaft. Just as mentioned earlier, it converts the linear motion of the piston into rotary motion of the crank. One of its end parts is attached to the piston through a piston pin also known as gudgeon pin and wrist pin. It other end is attached to the crankpin journal using bolts to hold down the upper and lower bearing caps called the big end.

The bearing is in the form of two half-shells placed in the crank journal by the big end connecting rod. Both ends are not rigidly fixed in order to rotate through an angle. Hence, both ends are in continuous motion and under tremendous stress from the pressure of the piston.

The connecting rod is generally made from forged steel and sometimes from aluminium alloy when lightweight and high impact absorbing ability is prioritized. The connecting rod is manufactured with a high degree of precision as it is a sensitive part that is prone to failure.

5. Cylinder head:

These engine parts serve as a cover to the cylinder block, valve, rocker arms and the ignition element. It is bolted to the cylinder block with the head gasket in between.

The cylinder head is made from cast iron and sometimes aluminium alloy when the lightweight part is needed and as it conducts heat more quickly than cast iron.

Join our Newsletter

In an overhead camshaft engine, the camshaft is placed in the head with the absence of pushrod arrangement for valve mechanism. Some other parts like the inlet, exhaust ports and the combustion chamber also have their space beneath the cylinder, making it form one whole engine component.

6. Camshaft:

This internal combustion engine components is a shaft containing a cam fitted on it. it functions is to control the valves directly by sitting over them or through the rocker arm and pushrod mechanism. The valve timing is determined by the size of the camshaft. That is, the opening and closing of valves are governed by the camshaft which is mounted on the crankshaft either directly through a reduction gear or indirectly through a pulley and a timing belt.

Camshaft coupled to the crank by the gear required a pushrod and tappet mechanism along with rocker arms.The camshaft is commonly made of chilled iron castings and billet steel used in making high-quality ones. The purpose of the chilled iron offers greater wear resistance and surface hardness.

7. Valves:

Valves as known as poppet valves on IC engines. It is made of a long thin circular rod named valve stem and a flat circular disk called valve head, which is tapered along the thin rod. The function of the valve is to enables of valve for a fresh intake of fuel and air and the releases of waste gases (exhaust.) The opening and closing of the valve are caused by the sliding motion of the camshaft and the associated linkages.

Engine valves are made from steel alloys filled with sodium to increase the heat transfer capacity. Finally, the valves are of two sections; intake/inlet valve, which allows fresh charge to enters the chamber when open and the exhaust/outlet valve allows the escape of the exhaust gases.

8. Rocker arm:

This internal combustion engine part plays an important role as it transmits the rotary motion of the cam or crankshaft through a tappet/latch and converts it into a linear motion of the valve stem, helping in depressing the valve head

The rocker head is made from steel stampings for light and medium-duty engines whereas heavy-duty diesel engine rocker head is made of cast iron and forged carbon steel as it offers greater strength and stiffness. The rocker arms oscillate about a fixed pivot rod in the cylinder head.

9. Crankcase:

These internal combustion engine components are located below the cylinder block containing the bearings that rotate the crank. This main bearing is a sliding bearing with adequate oil supply in it. Four-cylinder inline petrol engines contain three bearings in the crankcase, one at each end and one in the middle while in diesel engines have five main bearings, one at each end and one between each cylinder.

The crankcase is made from cast iron and aluminium the same material used in making the cylinder block. Crankcase serves many purposes to the engine as it helps to protect its inner mechanism from dust, dirt and some other materials. It also serves as housing that encloses the crankshaft and the connecting rod, keeping the oil and air.

10. Oil pump and sump:

The function of the oil pump is to pumps the oil to various parts of the engine for proper lubrication, cleaning and cooling. The oil pump in the engine is driven by the crankshaft gear. The oil is pressurized to various part of the engine components, which helps in lubricating and cooling the system.

The oil sump serves as storage containing a chamber that keeps the oil. The oil is lifted by the oil pump from the sump through a wire mesh strainer which keeps debris and dirt from entering the engine. The oil filter and oil cooler allow the oil to pass through before distributing it to the engine parts. The oil returns to the oil sump after doing its job.

Other automobile engine components are the electrical ones which will be discussed in another article. The electrical part of an engine includes:

  • Alternator
  • Starter motor
  • Spark plug
  • Electronic fuel injector
  • Ignition coil etc.

We hope you found this  “components of internal combustion engine” post useful and enjoyed the read. If you did, please consider sharing this post with your friends and students on social media. Thanks!


  1. Best place site to learn mechanics

  2. Thanks so much for the work atleast l can say my dream of becoming diagnostic technician is on the corner thank you so much am just a fresher starting with advance certificate in motor vehicle mechanic but due to covid19 things are not working out

Leave a Reply

Your email address will not be published. Required fields are marked *