What is a Cylinder Head?|Cylinder Head Definition and Function

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The cylinder head is one of the least noticed parts of a vehicle but among the most vital. In this cylinder head definition and function article, we will define a cylinder head, look at what it does, and its location in automobiles. We also included cylinder head definition images to help you recognize the component.

First, the cylinder head meaning in detail.

What is a Cylinder Head?

You may have heard about it. Most likely, you do not know what it is or even what role it plays in your car. So, what is a cylinder head, and what does it do? Here is the cylinder head definition and uses.

As its name implies, a cylinder head is the cast metal part that covers the top part of a cylinder. Here, we are talking about internal combustion engines. These are engines that use cylinders as chambers within which to burn fuel. As you can guess, electric cars do not have cylinder heads. They do not burn fuel unless they are the hybrid type.

The cylinder head mounts on the cylinder block or engine housing. Together with the piston and cylinder, it forms a part of the combustion chamber. Underneath the cylinder head lies the cylinder head gasket. The gasket seals the head to the cylinder block, preventing leaks. Here is a cylinder head diagram showing where the head and head gasket are positioned. Note also the engine block.

Cylider Head Parts

To help you understand these parts better, here is the definition of a cylinder block, head gasket, cylinder, and piston. Also, the combustion chamber definition and the parts that make the component.

Cylinder block– it is the part that forms the support structure for the engine cylinders and related components. Some people call it the engine block, although a technical difference exists between the two. Main cylinder block materials include cast iron and aluminum.

Cylinder head gasket– mounted between the cylinder head and engine block, the head gasket forms the seal between the two parts. Cylinder head gasket functions include containing coolant in the relevant passageways, preventing air and combustion gases from leaking, and maintaining compression of the engine cylinders.

Cylinder-thispart that forms the space for piston travel. The cylinder is where fuel burns to produce power. The number of cylinders varies depending on the type of engine. Generally, the higher number, the more the power.

Piston– a piston transmits the force of expanding combustion gases to the crankshaft. It is housed in the engine cylinder and usually made from an aluminum alloy. A connecting rod allows the piston to rotate the crankshaft.

Combustion chamber– it is the recess in the bottom part of the cylinder head. It forms the space where fuel burns to produce the force to move a vehicle. The cylinder is made up of cylinder walls, cylinder head at the top, and a piston at the bottom.

A cylinder head is found in the internal combustion engines of cars, trucks, locomotives, tractors, motorcycles, and sea vessels such as boats and ships. The heads vary in design. A cylinder head in motorcycle engines may be different from the type found tractors, for example.

In most cases, the engine cylinders and cylinder heads of bikes are one-piece structures. Large vehicles usually cylinder heads as separate pieces that mount on the engine block by means of bolts or studs.

Usually, the type of engine determines the kind of cylinder head to use. Inline engines use one cylinder head, while V and Boxer engine types have two different heads. In some heavy-duty motor vehicles, each cylinder has its own cylinder head. This makes cylinder head refurbishment or cylinder head exchange easy.

Here is a of different cylinder head’s functions in a car engine.

Cylinder Head Function

What is the function of cylinder heads in car engines? Although mostly unknown, the cylinder head plays an important role in the general operation of a motor vehicle. It is a complex structure consisting of many passageways. Each of these ports has a purpose to serve, and their collective roles define the importance of this engine part. Among the main cylinder head function in an engine are:

  • Provide the mounting structure for various components such as the inlet and outlet exhaust valves and ducts, spark plugs, injectors, and (in some head designs), the camshaft.
  • Contain the passages for coolant, oil, and combustion gases
  • Dissipate the heat produced by the engine and, therefore, produce cooling
  • Act as the combustion chamber seal and the engine’s mechanical control powerhouse
  • Take the compression resulting from combustion pressure
Clylinder Head Anatomy
Source: http://www.supras.org.nz

A cylinder head contains intake air, exhaust, Copland, and oil passageways.

One of the functions of a cylinder head is cooling the engine. The head achieves that using two main methods; water or air.

Water-cooled heads are the most popular, and many modern engines are of this type. In this type of engine, water is mixed with antifreeze to prevent the formation of ice. An anti-corrosion agent is also introduced to prevent the corrosive action of water. Water-cooled cylinder heads are more efficient and produce excellent results.

Air-cooled cylinder heads use large fins that fan the air to bring about cooling. They feature no cylinder head engineering complexities, which makes them inexpensive to make. Because cooling by air can occur in extremely low temperatures without the risk of freezing, air cooled-heads are more reliable. They are also lightweight and easy to repair.

Cylinder Head Materials and Manufacturing

Auto cylinder heads are cast from molten metal. Usually, manufacturers use the LFC , lost-foam casting,  for the cylinder head casting. The method uses polystyrene foam to produce the required pattern. It is one of the simplest processes for complex castings but also one that produces excellent results. Lost-foam casting has the advantage of dimensional accuracy and good finish, among other benefits.

Cylinder heads can be made from iron or aluminum. It depends on the required performance, durability, and other factors. Each material offers specific advantages that suit particular situations, as we shall see next.

Aluminum Cylinder HeaD
Source: http://www.ebay.ca

Aluminum cylinder heads- Aluminum produces lightweight heads that also dissipate heat more efficiently. However, cylinder heads made of aluminum are more expensive. In addition to the high cylinder head cost when aluminum is used, there is the issue of durability. Aluminum cylinder heads are weak structurally. They are easily damaged by temperature extremes, corrosive materials, and impacts.

Because they give better fuel economy and heat transfer, aluminum heads are often used in performance and race cars. In these cars, weight saving and rapid engine cooling are necessary features. Most gasoline engines use aluminum cylinder heads.

Iron Cylinder Head
Source: http://paceperformance.com

Iron cylinder heads- iron cylinderheads are less expensive than those made from aluminum. They are also high-strength and durable. The problem with engine cylinder heads cast from iron is that they are too heavy. They add to a vehicle’s weight and contribute to poor fuel economy.

Iron heads also transfer heat poorly and do not fit demanding applications such as race cars. These types of heads are mostly used in diesel. A diesel engine cylinder head costs less, stands up to damage better, and lasts a long time. Unless situation demands it, these are most preferred type of heads.


Cylinder heads are the mechanical powerhouses of internal combustion engines. They provide the space to install necessary engine parts. Passageways too, for crucial gases and liquids to get in and out of the engine. Many people do not understand the function of cylinder heads in a car engine, or even its location. This article contains information about the topic, from the cylinder head definition, automobiles that use it, to the materials used to make the components. Read more about the cylinder head in our other articles.

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