Cylinder Heads Guide – Explanation, Common Problems

Cylinder Heads Guide – Explanation, Common Problems

Cylinder heads are very common parts in internal combustion engines. And it is one of the biggest and most important structural parts. Here we explain the general purposes of these parts. You can find detailed information about these topics here;

  • What is a cylinder head?
  • What are their types and configurations of them?
  • General materials.
  • Manufacture of them.
  • Common breakdowns and problems.
  • FAQs

So, you can find lots of detailed information about cylinder heads to get to know about them. This article is mainly for new drivers, people that dealing with internal combustion engines, and people trying to take a driving license. This is a very valuable guide to getting to know about these parts.

What is a Cylinder Head?

Image Source: Wikipedia.com.

Cylinder heads are the structural parts of internal combustion engines. We place these parts on the engine block to obtain complementary parts for the engine cylinders. The general structure of the top of the cylinders in general.

As structural parts, these parts are the locations of common other important engine parts. 

In the structures of these systems, there are inlet and exhaust passages which are very important for an engine. From the inlet passage, the fuel-air mixture comes inside the cylinders. And from the exhaust passage, the burnt fuel goes to the outside.

Some valves control the inlet and outlet airs inside and outside on engines. So, you can find the places of valves on cylinder heads. We attach the inlet valves and exhaust valves to the cylinder heads.

Camshafts are also another important part of engines that we place on the cylinder head. The rotation of the camshaft controls the opening and closing actions of intake and exhaust valves.

Above all, cylinder heads provide structural support for spark plugs and fuel injectors.

As you see above, the existence of these parts is very important for an engine. We place the most important parts that provide the work of the internal combustion engine. So, the design of these parts is very complicated.

Different Configurations of Cylinder Heads

In the internal combustion engine technology, there are different configurations of these parts. The configurations are generally defined by the locations of the camshaft, intake, and exhaust valves.

Flathead Sidevalve Types

In these types of engines, the place of the intake and exhaust valves are on the engine blocks. So, these parts do not contain the valves in their structure. In addition, the location of the camshafts is at the engine block. And in these types, the structure of cylinder heads is simple.

In history, this type of cylinder head configuration was very common in automobiles. But today, it is not common.

Inlet over Exhaust Types

In these structures of engines, the location of the camshaft is at the engine block again. And also, the location of the intake valves on the cylinder head. And the location of the exhaust valves at the engine block again.

In around the 1900s, this configuration cylinder head and engine block configurations were very common. And they are more efficient than the side valve types.

Overhead Valve Types

In these types of internal combustion engine configurations, the place of the intake and exhaust valves are located at this part. And also, the location of camshafts is at the engine blocks.

The use of these configurations started in the 1960s today. Some of the car brands are using overhead valve types in engine configurations.

Overhead Camshaft Types

In these configurations again, all the intake, exhaust valves, and camshafts are on the cylinder heads. So, cylinder heads take the most general and complex configuration that they have.

In today’s engine technology, they use overhead camshaft types in most modern cars.

As you see above, the transfer of intake and exhaust valves and camshafts take place to the cylinder heads. So, they take their last shape in the latest technologies.

Also, the number of cylinders and engine cylinder configurations are very important parameters in the structure of these parts. For example, in a V8 engine, there are 16 valves, 8 spark plugs, and 2 camshafts. So, they have a very complex shape in these types of engines.

General Materials on Cylinder Heads

First of all, we need to know which kinds of properties we are seeking from them. The material of these parts must be very resistant to high temperatures. Because there is combustion right beneath them. Because of this temperature, their shape or integrity does not change.

Also, cylinder heads must be mechanically strong. Because there are lots of different mechanical loads on the engine heads because of the movements of pistons. So, it is very important to have good toughness and resilience.

And also, the manufacturability of these parts must be good. For example, the material must be very good in terms of metal casting operations.

Furthermore, cylinder heads generally have very complex shapes. After the casting operations to obtain these complexities, we need to apply extra machining and finishing operations to obtain very good surface finishes for some sections. So, if we think about all of these aspects, the general materials that we use; are aluminum alloysmagnesium alloys, and cast iron.

Cast Iron

Cast iron is one of the most common materials in the production of cylinder blocks. The most important characteristic of cast iron, they have very good casting capabilities. We can give different kinds of shapes to cast iron materials. And also, we can apply machining operations to obtain the holes and other geometries to attach other parts.

Also, the mechanical capabilities of cast irons are very good. They are very tough materials and they have very good vibration damping characteristics. And also, the thermal characteristics of cast iron materials are superior. Their thermal conduction characteristics of them allow very good cooling of these materials in cylinder head applications.

So, these materials are very common in the casting of big size engines. A

Aluminum Alloys

Also, the advanced properties are the same as the aluminum alloys. The only difference between the aluminum alloys from cast irons, they have lower mechanical properties. And also, they have lower densities. So, in lightweight engine applications where very big mechanical requirements are not needed, aluminum alloys are in use.

For example in car and motorcycle engines, the use of aluminum alloys is the most common one.

Magnesium Alloys

Around these three materials, magnesium alloys are not common in use. But in special applications where heat rejection is of prime importance, they use these materials. And also, they are very low in weight.

So in the little size applicationsi, there are different applications engine heads from magnesium alloys.

These are the general materials that they use in the production of cylinder heads.

Manufacture of Cylinder Heads

Cylinder head casting model.
Casting model of cylinder head(Image Source: Yamaha.com).

You know that the geometries of cylinder heads are very complex shapes. Because, there are different other parts that we attach to them such as camshafts, intake and exhaust valves, spark plugs, and fuel injectors.

So, the most important manufacturing technique of them is metal casting.

In metal casting, they prepare the model of the cylinder head from wood or foam. Also, they add an extra shrinkage ratio to this model. And they place this model into the sand. And we obtain the sand mold of the cylinder head. At the end of the casting, we obtain the general shape of the cylinder head.

After the sand casting and solidification of these parts, they apply extra machining and finishing operations on them. These operations are generally honing or finishing the holes where the fluid and oil flow take place. And also, the attachment places of other parts are finished to obtain the required geometry.

In the market, there are different manufacturers of cylinder heads. According to the type and model of your engine, you can buy one of them from these manufacturers.

Common Problems and Breakdowns of Cylinder Heads

Possible cracks.
Image Source: Enginebuildermag.com.

Cylinder heads are structural parts. And in general, there are no complex breakdowns of them. You can find the most common failures of these cylinder heads. But the most common failure or breakdown of cylinder heads is cracking. You can check the general failure reasons of them here.

Coolant Leaks from Cylinder Head

Coolant or water is circulated through the structural parts of engines. One of these structural parts is cylinder heads. If there is a coolant leak on your cylinder head, this means a possible crack on your head.

Coolant leaks can lead to the problem of overheating after a while. Because the coolant gets drained from the cooling system, there is no heat rejection system which will cause engine failure. You can check the heat of the engine light.

Overheating of Engine

As we stated above, the overheating of an engine is a general problem that can be caused by several reasons. But the most important reason is the coolant leak or breakdowns in the cooling systems of the engine. If there is an overheating, you need to directly check the cooling system of your engine.

And also, one of the possible problems is the cylinder head crack. Coolant can leak from these cracks and lead to the overheating of the engine.

Thermostat Problems

The thermostat is also a very important part of your car engine. It measures the temperature of your engine and allows the coolant into your engine. But coolant does not always circulate. If the temperature of the engine rises, the thermostat opens and allows the coolant to circulate through the engine.

So, if there is a problem with the thermostat, the engine overheating can be a problematic issue. And because of the engine heating, cracks can form on the structure of the cylinder head because of the thermal shocks. So, you need to take special care of the thermostats.

Air in the Fluid Circulation System

Also, cylinder head cracks can cause the air in the circulation system. And if there is air in the fluid circulation, the temperature of the engine will raise.

Water Pump Breakdowns

Even the water pump breakdowns can cause cylinder head cracks. Because, if the water pump does not work properly, the coolant fluid does not circulate. And engine heat rise-ups can cause possible cylinder head breakdowns.

Conclusion on Cylinder Heads

As you see above, cylinder heads are very important parts of our engines. Because they are structural parts with engine blocks. They contain other elements such as camshafts, intake and exhaust valves, and spark plugs. So, they provide a very important duty in engines.

If we take a look at the historical change in the structure of these parts. Firstly, all these parts are located on the engine block. But transferring these parts took place completely to cylinder heads.

Also, the general materials of these parts have very special properties such as mechanical strength, good thermal characteristics, and the ability to manufacture with casting operations. So, cast iron, aluminum alloys, and magnesium alloys are the most common materials.

Furthermore, the general manufacturing technique of these parts is sand casting operations. Also, additional finishing and machining operations are applied to these systems.

It is very important to know the general problems of cylinder heads. And fixing of these problems changes according to the type of problems. But the most general problems are arising because of the overheating of the engine.

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FAQs About Cylinder Heads

What do cylinder heads do?

The most important duty of them, they constitute structural support for the attachment of other engine parts such as intake and exhaust valves, camshafts, spark plugs, and fuel injectors. So, they are very important complementary parts to the engine blocks.

What is the cylinder head on a car? 

The cylinder head is a structural part of a car that is placed on top of the engine. It supports the important parts for the combustion in engine cylinders. So, they are a very important structural part of your car engine.

What does a cylinder head damage?

Among the most possible damages to these parts, overheating of the engine. Because of the overheating, thermal shock may take place and cracks can form. So, it is very important to check the cooling system if there are cracks on cylinder heads.

How much is a cylinder head? 

It changes according to the type and size of the engine. But for most car engines, it changes between $1000 to $3000 according to the material, complexity, and car. Also, you need to add the expertise of the attachment of these parts on your engine which is generally between $500 to $1000.

How much does it cost to fix the cylinder head?

The general problem of the cylinder heads is the cracks. If they can solve this crack with the welding operations, you will probably pay $500-$1000 for the labor costs. Also, if they will change the total cylinder head with a new one, you will probably pay up to $5000.

Can a cylinder head be repaired?

Yes, it can. But it depends on the place of the damage. If the place of the damage is an unrepairable place with welding operations, it is very hard to repair it.

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