The cylinder head is the top part of the engine, which seals the combustion chambers from above. In modern engines, it also houses the valves and camshafts . That's why it's one of the most important mechanical components of our car.
This is one of the three basic parts that make up a piston combustion engine . Listed from bottom to top, they are: the crankcase, which houses the crankshaft driven by the connecting rods that go to the pistons; the engine block, which is the middle part where the combustion chambers are located and where the pistons move up and down; and finally, the cylinder head, which closes the engine at the top.
cylinder head parts
The cylinder head itself has few parts, although inside it contains many parts necessary for the operation of the engine. In general its parts are limited to four:
- cylinder head cover: upper part that covers the cylinder head and keeps the oil inside to keep everything lubricated.
- cylinder head cover gasket: is responsible for maintaining the seal between the cover and the head
- Head: This is where the camshafts, valves, etc. are located.
- head gasket: is responsible for maintaining the tightness between the cylinder head and the block.
What's inside the butt
Although they are not parts of the cylinder head itself, inside it we find the camshaft (s) , the intake and exhaust valves , the guides where the valves move up and down, the springs that allow the valves to close again when the camshaft opens them, in some cases rocker arms to actuate the valves, seals and half-cones to fix everything in place, and retainers to prevent any part from damaging the cylinder head.
Furthermore, the cylinder head is where the spark plugs are located in gasoline vehicles or the glow plugs in diesel vehicles. Similarly, the cylinder head also houses the fuel injectors , which allow fuel to be injected into the cylinders.
We also cannot overlook the lubrication system of the cylinder head, as it is crucial that the camshaft and valves are properly lubricated to ensure the engine's smooth operation. Therefore, it also has one or more O-rings to prevent oil leaks . As for its attachment, it is bolted to the engine block using high-strength bolts. Between the cylinder head and the block, we find the head gasket.
cylinder head types
air or liquid cooled
Depending on the engine type, we can find different types of cylinder heads. Firstly, they can be differentiated based on whether the engine is air-cooled, in which case they have cooling fins, as found on some motorcycles. Secondly, if the engine is liquid-cooled, the cylinder head design is much more complex to ensure the coolant flows evenly and dissipates heat uniformly. Otherwise, unwanted deformations could occur, potentially leading to damage.
Depending on the number of valves
We can also find cylinder heads with two valves per cylinder or models with four valves per cylinder. We can even find other, more unusual configurations, such as five valves per cylinder. The number of valves per cylinder directly affects engine performance.
There are also very old combustion engines that did not have valves in the cylinder head. These are the so-called Side Valve (SV) distribution engines, which had the valves in the engine block, on the sides of the cylinders. An example of this type of motors are those that mounted the famous Ford T of the beginning of the XNUMXth century.
According to the material
The materials used to construct a cylinder head can vary. Most commonly, it is made of steel, aluminum , or an alloy . This material doesn't necessarily have to be the same as that used for the engine block, although it often is.
Aluminum cylinder heads have the advantages of conducting heat better and being lighter. However, their disadvantages are that they are more expensive and less resistant to long-term wear. This conductivity has another important effect on engines: lower thermal inertia. In simpler terms, this means that the faster the metal heats up, the faster it cools down. The result is that it reaches operating temperature sooner but cools down more quickly.
Steel cylinder heads, on the other hand, weigh more and have greater thermal inertia. They are also cheaper and more resistant to wear over time.
Breakdowns
Together with the block and the engine block, the cylinder head forms a structure that must withstand the enormous pressures and temperatures generated inside. They are joined together by high-strength bolts and gaskets that ensure there are no cracks.
When an engine overheats, a very common problem is cylinder head warping or a loss of sealing due to a blown head gasket . This is because, as the part that seals the combustion chambers from above, it is the one most affected by excessive heat. Therefore, cylinder heads must be very tightly secured to prevent any sealing problems.
car engine cylinder head price
The price to repair or replace a cylinder head is high, both due to the cost of materials and the number of hours required in a workshop. If it's just the gasket, the price of the materials might be around 100 or 200 euros , but if the cylinder head itself also needs replacing, the price can rise to nearly 800 euros.
Workshop hours can range from 10 to 20 hours of work depending on the model, which can increase the bill by between 400 and 1.200 euros depending on the workshop you go to.
Images 3,4 and 5 – LC Nøttaasen Follow, Timitrius, Mirko Junge