Internal Combustion Engine – 101

Internal Combustion Engine – 101


Explained and illustrated in this article are the various components making up an internal combustion engine, and each component’s function. 


Various scientists and engineers contributed to the development of Internal Combustion Engines, such as:

  • 1791 John Barber developed a turbine.
  • 1794 Thomas Mead patented a gas engine.
  • 1794 Robert Street patented and built an internal combustion engine using liquid fuel.
  • 1798 John Stevens designed the first American internal combustion engine.
  • 1807 Swiss engineer François Isaac de Rivas built an internal combustion engine ignited by electric spark.
  • 1876 Nikolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the compressed charge, four-cycle engine.
  • 1879 Karl Benz patented a reliable two-stroke gas engine.
  • 1892 Rudolf Diesel developed the first compressed charge, compression ignition engine.

The first piston engines did not have compression but ran on an air-fuel mixture sucked or blown-in during the first part of the intake stroke.  

Early Internal Combustion Engines were started by hand cranking, various types of starter motors were later developed.


Since these early days, the Internal Combustion Engine has been developed and refined to perform almost impossible feats of high power outputs and frugal fuel consumption,

This coupled with lightweight design by using new modern materials and methods of construction.

I will be sticking to the basics in this post and looking inside an internal combustion engine and looking at what makes it tick.

Main Components

(not exhaustive, emphasis on “MAIN”)


Engine Block

Engine Block

It is made of cast iron, hardened sleeves and has mild steel Welsch plugs. Houses the 4/5 main components of the engine block, namely the Crank Shaft, Pistons, Connecting Rods and Sump. It also houses the camshaft in an overhead valve engine configuration.

It has cast vertical cylinder bores housing the pistons and con-rods, lined with tempered steel.

The crank bolts in at the bottom of the block and is held in place by main bearing caps housing oil-lubricated white metal bearings. 

The engine block has coolant passages cast around the cylinder bores to allow for coolant circulation.

It also has oil channels cast in to allow for oil circulation pumped from the Sump to the Crankshaft and Cylinder head by the oil pump.

It houses the:

  • oil pump,
  • water pump
  • the fuel pump (if mechanical),
  • the distributor,
  • oil filter
  • camshaft
  • cylinder head.


Cam Shaft

It is made of cast iron and hardened steel. Opens and shuts the valves in the cylinder head. 

The Camshaft is bolted to the cylinder head in an overhead cam engine configuration, or inserted into the engine block in an overhead valve configuration engine, and is timed to the crankshaft via a timing belt or timing chain configuration.


Is made of cast iron to increase its weight and is housed in the bottom part of the engine block. Connects the pistons to the engine, via the connecting rods, running on oil-lubricated white metal bearings (Mains Bearings).

The Crank Shaft transfers power from the engine to the wheels of an automobile, through a flywheel, clutch assembly, transmission and driveshaft systems.

Crank Assembly
Crank Assembly

Connecting Rods

Made of hardened steel and connects the pistons to the crankshaft via oil-lubricated white metal bearings (crankpin bearings) allowing the conversion of reciprocating motion into rotary motion.


Made of cast aluminium. The top of the pistons forms the lower part of the combustion chamber and converts downward motion into rotary motion, by transferring power created when the air and fuel mixture combusts above the piston head, forcing it down by rapidly expanding gasses to the crankshaft via the connecting rods.

Cylinder head

Cylinder Head
Cylinder Head

Cylinder heads at cost!!

Forms the top part of the combustion chamber, where the air and fuel are burnt in a controlled implosion, Also houses the valves and camshaft in an overhead cam engine configuration. Is made of aluminium or cast iron.

Combustion Chamber

The space between the top of the Piston and the bottom of the Cylinder Head formed to create a combustion chamber sealed at specific times by the timed opening and closing of the valves housed in the cylinder head.

Fuel and Air Intake Manifold

Through which air and liquid fuel are delivered to the combustion chambers to be burnt and converted to power by the engine, made of aluminium or plastics. 

Intake Manifold
Intake Manifold

Manifolds at low prices 

Exhaust Manifold

The burnt air and fuel gases are forced into the exhaust manifold by the upward stroke of the piston and channelled into the automobiles mufflers/silencers to be released into the air made of aluminium and/or plastics.

Exhaust Manifold

Oil sump

Serves as a sealed reservoir to contain the engine oil used to lubricate the moving parts in the engine, made of aluminium, steel or plastics. 

Oil Sump

 Flywheel/Torque converter

Sustains momentum during the 3 non-power strokes, namely the Intake, compression and exhaust strokes, to keep engine momentum and power flow constant within the engine. It is made of mainly cast iron and/or steel.

Torque Converter

Front Engine Pulley

It is made of cast iron, steel and sometimes rubber dampers are incorporated to reduce vibration. Its function is to transfer power via fan belts to drive.

Front Engine Pulley

  • alternators,
  • power steering pumps,
  • fixed and viscous cooling fans
  • air conditioner pumps,

That is sometimes fitted to the engine of an automobile. 

How it all Works

There are 4 strokes which the internal combustion chamber engine cycles through, Namely:

  • Intake
  • Compression
  • Power
  • Exhaust

The 4 Engine Strokes

Intake stroke

Air and liquid fuel, (petrol/gasoline) is sucked into the combustion chambers of the engine via the inlet valves in the cylinder head by the downward stroke of the piston, in reaching the end of the inlet stroke’s downward movement the inlet valve starts to close thereby sealing the chamber.

Compression stroke

The air and fuel are compressed to approx. 1:16th of its original volume by the upward stroke of the piston thereby creating a highly volatile combustible mixture. The chamber is sealed during this stroke.

Combustion/Power stroke

At some point before the topmost cycle of the power stroke, a controlled spark is introduced to this volatile mixture, which creates an implosion causing the rapid expansion of the burnt gases which forces the piston in a downward motion, thus named the power/combustion stroke. 

The chambers are still sealed during this stroke but toward the end of the combustion/power stroke, the exhaust valve starts to open.

Exhaust stroke

With the following upward stroke of the piston, the burnt gases of the power stroke are forced out into the exhaust system through a now fully opened exhaust valve.

These strokes count as 1 cycle2 revolutions of the crankshaft – 1 revolution of the camshaft ) in a 4 stroke internal combustion engine and happen in the blink of an eye, the cycle is repeated constantly while the engine is running.

There are many other things happening in the engine while the 4 strokes are taking place and I will elaborate on them in posts to follow, stay “TUNED” to this site (excuse the pun).

#Learn More


If this post has made things clearer to you about what happens in your car’s engine while you are driving then I have succeeded in achieving my objective.

What are your thoughts, leave comments and suggestions below.

Until Next Time “Safe Motoring


Gary De La Cruz

I have been 30+ years in the motor industry, still hands on, and have great passion for my chosen profession, I learn new things each day and believe that "if you enjoy your work, you never have to work a day in your life"I believe in honesty, integrity and helping where help is needed.

This Post Has 10 Comments

  1. rue

    this is what I’m looking for
    clearly explained

  2. Oriyomi


    1. Gary De La Cruz

      Thank you for the endorsement, I am glad to be of service.
      All the best


  3. Harry

    This site is very nice with quality engines and guidence

    1. Gary De La Cruz

      Hello Harry

      Thank you for the visit to my website and the positive feedback, I am sorry I was absent for a while, but I am back now and am working on new materials for my website, improving its presents on the internet, so feel free to pop in periodically for new content and articles.

      I wish you all the best for your online and offline future.

      All the best regards

  4. Tim Gillen

    Omg I love your site. I remember wanting to understand internal combustion in high school but never being able to get it. You make it so easy! Not sure I get it yet though lol. Tim

    1. Gary De La Cruz

      Hello Tim

      Thank you for visiting my site and taking the time to comment,
      I am pleased that you found it educational and informative because that was my intention when doing this posts, please return and check out other informative posts here concerning all aspects of the maintenance, repair and workings of automobiles, when you have more time.

      Thankyou Time
      All the best

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