What is a Cylinder Head in Cars?

Every effective machine involves a plethora of impressive components that work behind the scenes to ensure optimal outcomes. While cylinders are the pivotal chambers where combustion takes place, a cylinder head securely encloses them to prevent gas leakage.

A cylinder head is a cover that encloses or protects the cylinder of an internal combustion engine. It is affixed on top of a cylinder block with the help of bolts and hosts an elaborate set-up with valves and a camshaft.

The cylinder heads have conspicuous grooves that allow seamless movement of exhaust gases and inject fuel in diesel engines. Furthermore, a special layer of asbestos and metal gaskets between cylinder and cylinder prevent any leakages. Cylinder heads are often made of an Aluminium alloy for efficient conduction of heat.

Here is an elaborate description of each of the parts of cylinder heads along with the respective functions of cylinder heads.

1. Cylinder Block

A cylinder block is the bottom part of engine cylinders that holds the essential components together. It acts as a base for an engine cylinder while allowing it to function smoothly.

2. Head Gasket

Head gaskets firmly seal an engine block and cylinder head thus preventing gases from escaping. It acts as a rubber seal and compresses an engine cylinder while allowing it to function seamlessly.

3. Intake and Exhaust Ports

An intake port allows air to flow into the combustion chamber of an engine. Similarly, an exhaust port connects to the exhaust manifold and expels the gases after the combustion process.

4. Cylinder Valves

Valves are essential parts of the cylinder head that allow the movement of air into a combustion chamber. They act as gates that open and close whenever needed, to allow optimal functioning of an engine. However, the diameter of the intake valve is more than the exhaust valve to allow maximum air movement.

5. Valve Spring

A valve spring firmly seals a valve and pulls it back into an accurate place whenever needed. Without a valve spring, a valve would remain open, leading to gas and fuel leakage.

6. Spark Plug

Spark plugs lie strategically in a cylinder head and initiate a spark that ignites the fuel and air mixture in a combustion chamber. The spark pushes down the piston creating power that ultimately allows an engine to function adequately.

7. Injector

Injectors are commonly found on a cylinder head of a diesel engine. A pump pushes up the fuel to an injector which then sprays it up to combustion chambers. This fuel mixture ignites to form power that runs an engine.

8. Camshaft

A cylinder head comprises a camshaft that is responsible for opening and closing the valves. Furthermore, a belt attaches this camshaft to a crankshaft. The crankshaft's rotational motion allows this camshaft to open and close the engine valves at the right time.

Here are the functions of a cylinder head:

• Cylinder heads provide a structure that holds important components like intake and exhaust valves, spark plugs, injectors and camshaft. These components are responsible for the adequate efficiency of an engine.

• A cylinder head provides a passage for the movement of coolant, oil and combustion gases.

• It allows seamless dissipation of heat thus cooling the engine and saving it from potentially serious damage.

• The cylinder heads form a firm seal for an engine’s combustion chamber.

• It accurately withstands the pressure that forms after a combustion process.

Depending on the positioning of ports and valves, there are several types of cylinder heads. Here are a few of them.

1. Loop Flow Type

In a loop flow cylinder head, the exhaust and intake ports are on the same engine side. So, the gases change their direction on their way out.

Pros

One of the positive aspects of a flow-type cylinder head is that the air and fuel swirl together which preheats the incoming or intake air. As a result, it allows seamless blending of air and fuel. Besides, a loop flow type cylinder head functions to clean out the remaining gasses.

Cons

Despite all these benefits, loop-flow type cylinder heads offer limited space for air and fuel flow. So, the engine does not receive adequate amounts of fuel for its combustion process, thus producing insufficient amounts of power.

2. Offset Cross-Flow Type

In a crossflow cylinder head, the exhaust and intake ports lie opposite to each other. So, air comes in from one side and exits from the other. Additionally, offset cross-flow type cylinder heads may use an overhead camshaft which directly controls valve movements. Besides, there is a valve-train system with camshafts in engine blocks. Pushrods and rockers transfer movements, thus opening and closing the valves.

Pros

An offset cross-flow type cylinder head functions better than a loop flow counterpart since the gases do not change direction. As a result, they may flow easily without additional hassles.

Cons

An offset cross-flow cylinder head comes with a few drawbacks owing to the position of ports. Since the intake and exhaust ports lie opposite each other, it may result in poor air-fuel mixing capacity thereby leading to poor engine performance.

3. In-Line Cross Flow Type

In-line cross-flow cylinder heads are almost similar to offset cross-flow types with a minor difference in the arrangement of valves. While the intake and exhaust lie opposite to each other, the valves incline transversely at an angle that ensures a smooth flow of air.

Pros

These types of cylinder heads ensure better performance and optimal efficiency of engines owing to the unique placement of valves.

Cons

Despite its optimal performance and efficiency, in-line cross-flow cylinders are difficult to manufacture and design. Moreover, the manufacturing process requires lumpsum investments. So, these cylinder heads are not convenient or feasible.

Easy to Manufacture

Cylinder heads involve simple components and are easy to manufacture, unlike other components and parts of an engine.

Alterable

You can change the thickness of the gasket that seals a cylinder head to an engine block, thus altering the compression ratio. This allows manufacturers to optimise an engine's performance.

Easy to Maintain

A cylinder head involves straightforward maintenance processes. You may easily decarbonise them to remove carbon buildup. Besides, the valve grinding process to firmly seal the cylinder head to valves is relatively simpler.

Here are some disadvantages of cylinder heads:

Carbon Freezing

Carbon freezing is a process that degrades the functioning capacity of a cylinder head. In this process, a layer of carbon accumulates on a cylinder head owing to improper fuel combustion and the presence of residues of oil.    

Scale Formation

Minerals in hard water often accumulate in an engine's water jacket, restricting water flow. This results in engine overheating since this mineral accumulation prevents the seamless movement of heat.

Cracking

A cylinder head is made of metals that expand on exposure to hot temperatures. So, on pouring cold water into an engine, a cylinder head may expand and form cracks. These cracks are detrimental to an engine's performance.

Here are some ways you can tackle some issues of a cylinder head.

Decarburisation

You can conveniently tackle carbon freezing with decarburisation. In this process, you open the cylinder head and clean it with a scraper to remove carbon particles.

Addition of Soda Water

Scale buildup often degrades an engine's performance and needs immediate attention. So, you can add soda water to the radiator and stir it for a while. Then, you will have to thoroughly clean it using the reverse-facing method to remove a layer of crust.

Reduce Thermal Stress

Cracking an engine part may have serious consequences. You may avoid cracking due to overheating by being mindful of the correct procedures. Besides, you will have to allow an engine to cool down naturally to avoid exposure to expansion due to temperature fluctuations.

Cylinder heads are made of two primary components. Here are their names and features.

1. Cast Iron

Cast iron is one of the primary components and materials found in an engine cylinder. It is a ferrous compound made by a combination of 2-4% carbon, less than 0.1% sulphur, 1-1.5% manganese and 2.5% silicon.

2. Aluminium Alloy

An aluminium alloy is another primary component that ensures the optimal functioning of a cylinder head. This alloy consists of iron, silicon, manganese, magnesium and zinc. While aluminium has a soft nature, these compounds add to the strength and firmness of a cylinder head.

Cylinder heads are made with a casting process where manufacturers pour molten metal into a mould to create a suitable shape for a cylinder head.

A lost foam casting technique using polystyrene foam is used to prepare the mould. This mechanism is ideal for creating complex designs with conspicuous shapes. Besides, manufacturers may use either aluminium or iron to prepare cylinder heads.

To conclude, a cylinder head plays a vital role in determining the efficiency and productivity of an engine. While they perform tirelessly to ensure engine efficiency, they are often susceptible to damage. So, you must be mindful of warning signs and take utmost care of cylinder heads to enhance their efficiency.