The head gasket of a car engine is a well-documented component, and many car drivers are aware of its functions, however, the functions of the cylinder head are less known. For this reason, we have put together everything you need to know about a cylinder head, including its role, different types and potential problems you may come across.
Why Does My Car Have A Cylinder Head?
A cylinder head forms part of the internal combustion engine in your car and is located above the cylinders of the cylinder block. Together, both parts form a combustion chamber with the interface between the two parts utilising a head gasket. Integrated into the cylinder head are passages and ports to allow air and fuel to be delivered to the combustion chamber. Additionally, some of the passages allow the exhaust gases to escape.
Ensuring the combustion chamber (cylinder) is constantly lubricated is another rôle of the cylinder head. Lubrication of the cylinder is important because it allows the engine to operate smoothly, making the cylinder head a critical part of the function of a car engine.
What Does A Cylinder Head of and How Is It Built?
The cylinder head is one of the most expensive components of the engine due to its requirement to operate at extreme temperatures and its complex geometry. The extreme operating temperatures due to combustion means the cylinder head is made from materials such as aluminium alloys.
The cylinder head is anchored to the crankshaft housing, and a valve cover sits on top of the cylinder head to close it off.
Types Of Cylinder Head
Flathead Cylinder: A flathead cylinder is the oldest and simplest design of cylinder heads. The primary rôle of the flathead cylinder is to protect the cylinder block. Due to their age and simplicity, they do not allow the engine to perform efficiently making them unpopular in modern cars.
Overhead Camshaft Cylinders Heads: Overhead camshaft cylinders are the most advanced type of cylinder head available. As the name suggests, this type of cylinder head incorporates the camshaft, removing the need for pushrods. Additionally, the design integrates channels and allows for better airflow making it more efficient.
Overhead Valve Cylinder Heads: This type of cylinder is superior to a flathead cylinder, however, not an overhead camshaft cylinder head. Overhead valve cylinder heads have the camshaft above them, meaning they require pushrods and valves to provide more efficient airflow.
How Does A Cylinder Head Not Overheat?
As mentioned above, cylinder heads operate at very high temperatures due to the combustion process of an engine. Therefore, it is critical that the cylinder head does not overheat, but how is this achieved? Cylinder heads are cooled via two different methods described below :
Water Cooled Cylinder Head
The majority of modern engines now use a water cooling system to keep the cylinder head at suitable temperatures. The water contains a frosting agent to prevent freezing overnight, and the fluid is transported through the passages integrated into the cylinder head to take away excessive heat.
An advantage of this type of cooling system is that the fluid can absorb and dissipate a large amount of heat, making it one of the most effective cooling systems.
Air Cooled Cylinder Head
Air-cooled cylinder heads are cooled by passing air and require cooling fins to direct the air over the cylinder head. The key advantage of this type of cooling system is its simplicity. It is a reliable cooling system that is cheap and requires little maintenance. Unlike water-cooled cylinder heads, this method means you do not have to worry about the water becoming frozen.
The Most Common Symptoms of Cylinder Head Problem?
Due to the nature and multifunctional purpose of a cylinder head, it is natural for problems to arise.
Defective Head Gasket
A defective head gasket is one of the most common problems that arise with a cylinder head. The root cause of this issue is wear, in particular abrasion. The head gasket is clamped between the head cylinder and cylinder block, acting as a seal. If an increased wear rate is seen on the head gasket, it will not be able to perform its primary function as a seal and hence result in a leak.
Overheating
Another most common symptom of a car engine cylinder head is overheating. The cylinder head is put under pressure due to the nature of the combustion process and can harm the efficiency in which the coolant is passed through the cylinder head. As a result, the head cylinder overheats and the shape distorts. To prevent overheating from occurring, coolant levels should be checked and maintained regularly.
Poor Engine Performance
Poor engine performance is a clear indicator that a problem with the cylinder head has occurred. It can result from a crack in the cylinder head having a detrimental effect on the engines ability to burn fuel. The issue will be very clear and easily identifiable when driving your car.
Low Coolant Levels
A low coolant level can result in a leak at the cylinder head, which will be easily identifiable. A crack in the cylinder head could be the source of the issue which will then have a knock-on effect and result in the engine overheating.
Shall I Repair or Restore The Cylinder Head
Due to the complexity of the cylinder head, repairs tend to be expensive. Fortunately, repairs or restorations of cylinder heads are frequently performed and well known.
After performing a repair, the cylinder head is generally ground flat to ensure that it seals effectively with the cylinder block. A complete change out of a cylinder head is rare as most repairs are centred around parts such as valves that are easily accessible.