What is a Cylinder Head?

Meaning | Concept | Definition:

Internal combustion engines typically include a cylinder block, which houses the pistons and the cylinders through which they move, and a cylinder head to cover the block. Certain engine configurations have multiple cylinder heads, each of which sits on its own bank of cylinders.

On some engines, such as the flat head type, the cylinder head may be very simple and designed solely to provide a sealed, removable top end for the head. Other engines have part of the valve train, or both the valve train and the camp shaft, inside the head.

In either case, the cylinder head is usually mounted to the block with a metal or graphite head gasket, turning the cylinders into sealed combustion chambers.

Cylinder heads are an important part of a combustion engine.

Simple engines such as those used in lawnmowers and in-line engines such as the L4 and L6 units have a single cylinder head to seal off all the combustion chambers. Other common engines, such as the V6 and V8, contain two parallel banks of cylinders.

This requires two cylinder heads, mounted in such a way as to have the appearance of a V, to seal the cylinder block. Another type of engine that uses two cylinder heads is the flat or boxer engine. This configuration is similar to the V-formation in that both banks of cylinders are driven by a single crankshaft, although, in the case of the flat engine, the banks are aligned in the same horizontal plane.

The complexity of a cylinder head largely depends on the type of engine it is used in. Many early automobiles used what is known as a flathead engine.

As the name implies, these engines used a head that was a simple flat panel, mounted through the head gasket, to a cylinder block that contained the entire valve train. The cylinder heads in these applications still performed the vital function of sealing the combustion chambers, although they lacked much of the functionality found in more modern units.

Modern cylinder heads are typically used in overhead valve (OHV) or overhead cam (OHC) configurations. A cylinder head on an OHV engine typically contains valvetrain components such as pushrods, poppet valves, and other components that are operated by a camshaft located in the cylinder block.

By contrast, OHC engines have the overhead camshaft, making it an even more complex unit. These types of cylinder heads usually contain the entire valve train.

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