1.-Block

This is the basic structure of the motor, this is the place where the cylinders are lodged as well as the crankshaft and camshaft etc. All of the other parts of the motor are mounted on it. They are generally of cast iron or aluminum. 
The cylinders could be in a line or in the form of a V. It has a series of openings or casings  where the cylinders are inserted as well as pushrods from the valve mechanisms, coolant conducts, cam shafts,  bearing bench supports, and in the upper part they include some drills where the cylinder head set isclamped.

2.-Crankshaft

This is the mechanical component which changes the alternated movement into rotational movement. It is mounted on the main lubricated bearings block.  
The crankshaft could be considered as a series of small cranks, one for each piston. The radius of the crankshaft determines the distance which the piston rod and the piston can move. The piston stroke is twice the amount of this radius.

3.-Crank

This is the element of the motor which closes the cylinder in its upper part. They can be made of cast iron or aluminum. It works as a support for other elements of the motor such as: Valves, hanging scaffolds, and injectors, etc. The holes for the tightening screws are located  between the crank and the block, as well as the entry screws for air through the induction valves, the outlet of gases through the exhaust valves, the entrance of fuel throughout the injectors, rod pitch of valve push rod of the valve rocker arm, and the passing of water between the block and the refrigeration cylinder head, etc.
Between the crank and the block of the motor there is a joint mounted which remains pressed against them, and to which we often refer to as the head gasket.

4.-Pistons

It is a cylinder plunger which goes up and down sliding along the interior of the cylinder of the motor.
They are generally made out of aluminum; each one generally has two to four segments. 
The upper segment is used for compression and is designed to avoid gas leaks. 
The lower segment is used for lubrication (with grease), and is designed to clean the walls of the oil cylinder when the piston carries out its descending stroke. 
Any other segment could be used for compression or lubrication, it just depends on the manufacturer design. 
They have a wrist pin which serves as the union between the piston and the piston rod.

5.- Sleeves

These are the cylinders throughout whose interior is where the pistons circulate. They tend to be of cast iron and have their interior surface hardened by induction and is polished afterwards.
They normally tend to be interchangeable in order to re-build the motor placing in some new ones, even though in some cases they can come directly mechanized into the block and in that case repairing becomes more complicated.
When the re-changeable sleeves are of the humid type, in other words, in motors cooled by liquid, they tend to have some slots in the bottom where you insert some rubber toric rings to close the water cooling chambers, and in its upper part is a tab which is inserted into a recess of the block in order to ensure perfect settlement. 

6.-Segments

These are metallic circular auto tightened pieces, and are mounted on the slots of pistons to serve as a mobile gasketed seal between the combustion chamber and the crankcase. Such seal is done between the walls of the sleeves and the pistons, in such a way that the piston and the piston rod sets convert the expansion of exhaust gases in useful work in order to make the crankshaft turn. The piston does not touch the walls of the cylinders. This closure effect should be carried out in conditions that vary in speed and acceleration. The segments prevent an excessive loss of oil produced upon passing to the combustion chamber, while leaving on the walls of the sleeve a fine coat of oil for lubrication.

Therefore, the segments carry out three functions:

* They hermetically seal the combustion chamber.
* They serve as a control for the  oil film which is existent in the sleeve walls.
* They contribute to heat dissipation, so that it passes from the piston to the sleeve.

7.-Piston rods

The piston rods are what connects the piston and the crankshaft, transmitting force from one to the other. They have two bushings so that they can be able to turn freely around the crankshaft and the bolt that connects them to the piston.
The piston rod should absorb the dynamic forces necessary to put the piston into movement and stop it at the beginning and at the end of each stroke. Thus, the piston rod transmits the force generated in the explosion stroke to the crankshaft.

8.-Bearings

This could be defined as a support for a crankpin. It should be robust enough as to resist the efforts of which it will be exposed to during the explosion stroke.
The crankshaft main bearings are lubricated under pressure and they have a hole on their upper part through which the supply of oil which comes from a conduct of lubrication from the block.
It has a slot which works to spread in a better and faster manner the oil throughout the area where the bearing operates. It also has some stubs which the bearing caps place into the corresponding block slots. Such stubs align the bearings and prevent that they move frontward or backwards due to the effects of the driving forces that have been created. The lower half that corresponds to the cap is smooth.
Besides those of the base, all of the motors have a thrust bearing which avoids the axial play in the extremities of the crankshaft.
Another type of bearing is the one used in the brake equalizer shafts; which is in the shape of a bushing shell, and of one sole piece. The hole for the oil coincides with the block lubrication conduct.

9.-Valves

The valves open and close the inlets and exhaust vent at the proper moment of each cycle. The inlet tends to be of a greater size than the exhaust vent.
The following parts are distinguished on a valve:

·         * Valve Base
·         * Stem
·         * Head 

10.-Distribution gear

It drives the accessories and maintains the rotation of the crankshaft, camshaft, the cam shaft of the injection pump, brake equalizer shaft in the proper de-multiplication rate.
The gear of the crankshaft is the motor gear for the rest which make up the distribution train, by which they should be synchronized amongst each other in such a manner so as the marks which they carry inside each one of them coincide.

11.-Oil pump

This is located in the rear of the motor in the oil case. Its mission is to pump oil in order to lubricate bearings and moving parts of the motor.
The pump is sent through a gear, from the camshaft and makes the oil circulate throughout small conducts in the block.
The main flow of oil is for the crankshaft, which have some drills that which direct the lubricant to the bearings of the piston rod and to the main bearings. Lubricating oil is also sprayed on the walls of the cylinder beneath the piston.

12.-Water pump

In the motors refrigerated by liquid this piece is in charge of  making the coolant flow throughout the motor block, cylinder head, and the radiator, etc.
The circulation of the coolants through the radiator transfers the motor heat to the air that circulates in the radiator cells.  A fan moved by the same motor makes the air circulate through the radiator.

13.-Vibration dampers

Two types of vibrations are originated in a motor at the expense of the forces created by the inertia of the spinning pieces and of the force developed in the explosion stroke.

·         * Vertical vibrations
·         * Torsional vibrations

14.-Dampers

All motors produce torsional vibrations due to the momentary torque due to the force developed in the explosion stroke and its recovery throughout the rest of the cycle.
Even thought the steering wheel is designed with enough size and mass so that its inertia maintains a uniform spin, absorbing energy in the spinning impulses and returning it throughout the rest of the cycle; it doesn’t avoid distortion of the crank during the acceleration. 
Thus, another device is used in the other end of the crank, called vibration damper whose object is to create an equal torsional force with a direction contrary to the one that occurs during explosion, to cancel its effects.

There are two types of shock absorbers or dampers:

1.      The first kind uses rubber as a shock absorbing material. The changing of pairs of the crank are absorbed by it, and the energy is dissipated in the form of heat. Therefore, a way of proving if a damper works well is to note if it is hotter than the rest of the pieces of the motor which surround it.

2.      The viscosity type absorber is basically made up of by a heavy crown, lodged in a fixed storage unit at one end of the crank, being able to move freely within it upon being suspended in a fluid (silicone). This crown tends to oppose itself to any subtle change of speed, transmitting this resistance throughout the fluid to the casing, and therefore to the crank, counteracting or absorbing the torsional vibration.