The cylinder head serves a vital role in the working of IC engines. However, its function is rarely mentioned when discussing engine operation. This first section takes you through topics to help you understand the part. These include cylinder head meaning, location, and function. Cylinder head parts too, and what they do. I will also be discussing the component’s price ranges across different manufacturers.
Cylinder Head Definition
The cylinder head of an engine is the part that attaches to the cylinder block. In other words, it’s the component that covers the cylinders and forms part of the combustion chamber. It’s also sometimes simply called “head”.
Engine cylinder heads are usually either cast iron or aluminum alloy. Aluminum is the most used cylinder head material today. However, a good number of diesel vehicles use cast iron heads due to their superior strength and ability to contain the higher compression pressures.
The cylinder head assembly attaches to the engine by means of bolts or studs. In order to provide a perfect seal, the space between the head and the engine block is usually placed a gasket. This is commonly called the cylinder head gasket.
Visually, the cylinder head in engine assemblies is a cast metal block with many passageways and ports. These consist of channels for oil, coolant, and gases. There are also seats for vital components such as valves, injectors, and spark plugs.
Apart from the channels and seats, a cylinder head assembly contains recesses on the underside. This is the side that mates with the engine block. These form part of the combustion chamber, and are designed to withstand the heat and pressures. They also house the intake and exhaust valves.
The cylinder head is also either a one piece structure or multiple pieces. The type on your engine depends on the vehicle type and application. Heavy duty automobiles commonly use the multiple-piece cylinder head design.
An engine can also use a single cylinder head or two. If your car is fitted an inline engine, the head is a single piece. V-type or Boxer engines, on the other hand, use a cylinder head for each side of the cylinder bank.
You’re now familiar with the cylinder head construction and appearance. Next, let’s discuss its function or purpose.
Cylinder Head Function
The cylinder head purpose is often overlooked. However, it’s one of the most important. The head is one of the major sections of your car engine alongside the engine block and oil sump. As such, you can expect it to play a major role in the engine operation. The function of cylinder head assemblies is clearly explained below.
House Important Components
The head contains many different parts that the engine needs to work. These include valves (intake and exhaust), fuel injectors, and spark plugs. In some engines, particularly overhead camshaft engines, the head also houses the camshaft. The components described here are usually contained in special bores or depressions, others on the upper side of the assembly.
Form Part of Combustion Chamber
Your car cylinder head contains recesses on the lower side that mates with the engine cylinders. These are designed to form part of the combustion chamber, helping the engine to operate as required. This is one of the most crucial functions of head cylinder assemblies, and which make them indispensable engine parts.
Provide Conduit for Oil, Coolant, and Gases
As seen in the cylinder head images in this chapter, the component is provided with many channels or ports throughout its structure. These serve different purposes. There are passageways for oil, openings for coolant, and these that allow the flow of air into the cylinders and exhaust gases out.
One of the important cylinder head functions is to conduct away heat. Coolant and oil are always circulating in the head’s passageways and carrying away heat. The metal structure of the head itself also helps to carry heat away, thereby helping to cool the engine alongside the cooling effect of the oil and coolant. Although not common, some types of cylinder heads feature fins to help dissipate heat.
Bear the Compression pressures
Being part of the combustion chamber, the cylinder head block must contain the high pressures produced by the fuel air mixture. To enable that, it’s usually made strong enough through a casting process. It’s also held to the engine block tightly by means of bolts or studs.
To sum up the functions, the cylinder head determines engine operation in terms of:
- Fuel consumption
- Power output
- Exhaust emissions
Let’s now examine the head in more detail by looking at the components that make it.
Parts of a Cylinder Head
A cylinder head assembly is a complex piece that contains many parts. Each of these has a part to play in the working of the head. The components of a cylinder head include the many passageways for oil or coolant and the openings to insert valves and other parts, as listed below.
Oil and Coolant Passages
A cylinder head contains channels for oil and coolant. The oil primarily serves as a lubricant. It also provides cooling to the head and the engine parts that it lubricates. The coolant passing through the cylinder head passages is meant to take away heat and help cool the engine.
Intake and Exhaust Ports
The cylinder head also houses passages for intake air and exhaust gases. The intake ports guide air into the combustion chamber, while exhaust ports channel exhaust gases away to the exhaust manifold. These ports are among the most crucial cylinder head parts and located in recesses that form part of the combustion chamber.
Cylinder head valves are parts that open and close to let in air and fuel into the cylinders while allowing exhaust gases to exit the combustion chambers. These valves contain parts that are necessary to their operation such as valve seals, valve springs, valve spring retainers, valve guides, valve seats, spring seats, and valve lifers, and rocker arms. All these for part of the cylinder head components.
This is the part of a cylinder head that combines with the space above the cylinder to form a place for fuel mixture combustion to take place. The reaction then produces the power to propel your car forward. The size of the cylinder head combustion chamber varies across the different versions of the head.
Spark Plug Mounts
Spark plugs mounts are major components of a cylinder head assembly, but only found in the heads of gasoline engines. The mounts are threaded hollows that hold the spark plugs, the plug tips protruding in the combustion chamber. The thread helps form an airtight seal around the spark plugs, thereby helping to maintain combustion chamber pressures.
These are basically electronically controlled valves. Their primary purpose is to inject fuel into the combustion chamber. In the cylinder head of diesel engine assemblies, the injectors work differently from those of a gasoline engine.
In OVC (Overhead Camshaft) engine types, the camshaft forms a part of a cylinder head. It’s function is to open and closes the intake/exhaust valves in timed way. To allow a synchronized operation, the cylinder head camshaft connects to the crankshaft via a belt or chain.
Cylinder Head Gasket
Although an independent part, the cylinder head gasket is an essential component that a cylinder head needs to mount. It’s usually made from a thin metal piece and placed between the head and the engine block. Its purpose is to provide an airtight seal and prevent gases, oil, and coolant from leaking out.
After the cylinder head parts list, let’s see how much the product goes for in today’s auto parts market.
Cylinder Head Price: How much does a Cylinder Head Cost?
Before purchasing a cylinder head, it’s usually good idea to understand the price estimates. That way, you can search for deals, especially if shopping for the part online. It also helps you budget your spending. The cylinder head price is discussed below including the factors that influence it.
Car cylinder heads generally cost from $200 upward. There are pricier heads of course such those used in high-end car models. It’s not unusual to find a $1000 cylinder head, for example.
The auto cylinder head exists in different types, sizes, and configurations. These variations cause the price to vary widely. Manufacturers are also at liberty to set their prices. That means similar heads can cost different amounts.
Other factors that determine the price include the material used. Aluminum cylinder heads are generally more expensive that the iron types. The price also varies between an OEM and aftermarket cylinder head.
Just like with any other car part, it’s important to go for moderate or fair prices. A cheap cylinder head may not offer the required quality in terms of durability. A costly one on the other hand, may not be any better.
The engine cylinder head covers the cylinder block, enabling combustion and several other processes. The component also comes in different parts based on configuration, design, and other factors. After the definition, the next part of the guide explores the different types of the head out there. Their characteristics too, and the process used to manufacture them.