Four stroke engine and the engine cylinder block….

Before I begin going through the various elements of the car, I think we need to introduce terms and processes so that we build the engine in our mind, one piece at a time.

The most common engine in production for cars is the four stroke engine. This term confuses some, but its a relatively simple term. Four stroke simply refers to the process in which the engine runs and each stroke has a name. To give you an example, if I were to write down some instructions for someone to post a letter through my mailbox, I would write them down in steps (i.e. remove letter from bag, open letter box, push letter through box, close letter box). Each of these steps is a called a ‘stroke’ in an engine, so when we use the term ‘four stroke’ we simply mean the four steps of taking fuel and turning it in to energy that produces movement. The four strokes are Intake, Compression, Combustion, Exhaust. You’ll need to remember this.

1- Intake – The intake valves are open, the piston is moving from the top of the cylinder to the bottom and in doing so its sucking in fuel and air.

2- Compression – The intake valves are closed, the piston moves from the bottom of the cylinder to the top, compressing the air and fuel mixture.

3- Combustion – The air fuel mixture combusts (explodes) and the force of that explosion pushes the piston back down to the bottom.

4- Exhaust – The exhaust valves open, the piston is pushed from the bottom of the cylinder to the top, which in turn pushes waste gases caused from the explosion, out of the cylinder so the process can start again.

Below is a diagram of how these work.

4 stroke.gif

When we use the phrase ‘engine’ it’s often used interchangeably with component parts (specific parts of an engine) but the engine comes in two halves, a bottom part which is known as the ‘engine cylinder block‘ and the top half of the engine know as the ‘engine head‘.

In the engine cylinder block, there are cylindrical holes which are known as cylinders. The process four stroke engine process takes place in each of these four cylinders. Below is an image of a engine cylinder block with an arrow indicating where the cylinders are located.

engine cylinder block.jpg


Here is a great video to show you how a petrol (gasoline) engine works.


Don’t worry about the valves, connecting rods or any of the other stuff we haven’t covered just yet because we’ll cover it in a later blog.

Just to finish this post in it’s entirety, the engine cylinder block also has a number of other functions, which are mainly to allow other parts to be connected to it, but it also has passages built in to it’s body that allow coolant to flow through the engine to cool it down whilst it’s operating.

I should say at this stage, there is more about the engine cylinder block that needs to be talked about, but at the moment I’m starting with the basics. Once we have a working knowledge of how the engine cylinder block works we can move on.


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