Do you have an engine head that you need to replace, and you want to know if the engine heads from different engines are interchangeable? You’ve come to the right place, for we have researched this question and have the answer for you.
Some engine heads are interchangeable. There are V6 and V8 engines whose left and right heads are interchangeable. However, for the majority of engines, the engine heads are made for a specific engine only.
Let’s talk more about engine heads and which ones are interchangeable and why. Learn more about engine heads in the succeeding sections.
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What is an engine head?
The upper half of the engine is called the engine head—more commonly known as a cylinder head—while the lower half is called the engine block.
The engine head combines with the engine block to seal off the combustion chamber. You then install the head gasket between the engine head and the engine block to create an airtight seal.
To perform its task to seal the combustion chamber, the engine head must be sturdy enough to withstand an enormous amount of pressure and heat. It is made of cast metal to make it more resilient against the compressive force that comes from the combustion of fuel.
The engine head performs an important role in controlling the flow of air in and out of each cylinder. It is also responsible for the proper deployment of fuel into each cylinder.
To perform these two functions, the engine head has small channels that hold fuel injectors and valves. Because of this, the engine head has the greatest number of moving parts than any other area of the engine.
Many passageways in the engine head must connect with similar channels on the engine block. These channels are where the oil and coolant flow to provide the cooling and lubrication that the engine needs.
How engine heads are manufactured
Engine heads are made from molten metal. Manufacturers use polystyrene foam to create molds for the engine heads. Polystyrene foam is a popular material for casting engine heads because it produces accurate molds and a good finish.
Aluminum Engine Heads
Aluminum and iron are the most common metals that are cast into engine heads.
Aluminum has the advantage of faster heat dissipation and lighter weight which leads to better fuel economy. It is the popular choice for engines of race cars and performance cars. These two types of cars value weight and cooling efficiency.
Most gasoline engines are cast from aluminum.
The downside to using aluminum for engine heads is its higher cost and its weaker material strength than iron.
Iron Engine Heads
Iron engine heads are cheaper than aluminum engine heads. The main strength of an iron engine head is its higher material strength and durability. They can resist damage better and can last a long time.
However, the downside of iron engine heads is that they are heavy and dissipate heat more slowly than aluminum.
The heavier weight also makes engines with iron engine heads less fuel efficient. Slow heat dissipation makes them a poor choice of material for race cars and performance cars.
Engines with iron engine heads are commonly used in diesel engines.
Other Engine Components Found In The Engine Head
Another important engine component that is found in the engine head is the camshaft.
The timing belt provides power to the camshafts. The rotation of the camshaft opens and closes the valves that bring in the fuel and air mixture to run the engine. It also opens and closes the valves that push out the exhaust gases that are the byproducts of combustion.
The movement of the intake valves and the exhaust valves must match the movement of the cylinders. If the cylinder movement doesn’t match, the cylinder can move into position to take in fuel and air, but the camshaft closes the intake valve at that precise moment.
This will cause the cylinder to move to the next cycle of compressing fuel and air, but it does not have any fuel and air to compress.
Another important component that you can find in the engine head is the spark plugs.
Spark plugs are responsible for providing the spark that will ignite the fuel and air mixture after the cylinder compresses it.
Diesel engines have glow plugs that you can also find in the engine head. Glow plugs help diesel engines warm up to make them easier to start the engine.
Some diesel engines can be difficult to start because the mass of the cylinder block and the engine head absorb the heat that comes from the compressive force of the engine. This cooling effect prevents the ignition of diesel fuel.
The glow plug produces heat from electrical energy because of the electrical resistance in its tip. The hot tip ignites the diesel inside the engine even when the engine is still cold. This reduces the time that a driver needs to crank a diesel engine to start.
Are engine heads interchangeable?
The left and right engine heads of some engines are the only ones that have a chance to be interchangeable.
The casting of the engine head might look the same from the outside, but it can be different from the inside. The coolant and oil channels of the engine head should connect seamlessly with the same channels on the engine block for the engine to function properly.
Misalignment of the coolant and oil channels can quickly lead to engine overheating. Improper oil distribution will lead to piston wear.
And the channels are not the only things that should be the same.
The holes for components like the fuel injectors and spark plug must be in the correct location. If the holes for the fuel injectors are off, the path of the fuel can be blocked when the engine head is connected to the engine block.
The same is true for the spark plug.
Another aspect that would be off if the engine head and the engine block are not made for each other are the holes for the bolts.
The holes can be off, and you will not have a way to secure the engine head to the engine block. Another scenario is that the holes will line up, but the sizes are different. This will force you to use a smaller bolt that will not give a secure fit.
Without a secure fit, the engine head will not be able to do one of its more important functions—to seal the combustion chamber.
Without a proper seal, the coolant and oil can mix with the fuel that your engine burns. This can lead to engine misfires and a drop in the coolant level over time. Having less coolant will lead to engine overheating.
And since the coolant is half water, the presence of coolant inside the combustion chamber can damage internal parts of the engine like the fuel pump, filters, fuel injectors, and pistons.
How to replace the engine head?
Replacing the engine head is something only professional mechanics should do. We talked about how the engine head has the greatest number of movable parts in the engine in a previous section. You will have to remove all these moving parts before you can get to the engine head and remove it.
Why do engine heads need replacement?
The engine head and the engine block are among the sturdiest parts of the car. The engine head is made to seal the large amounts of pressure that combustion generates. This ensures that the majority of the energy from combustion will transfer to the crankshaft and then from the crankshaft to the rest of the drivetrain.
However, the engine head can crack when you expose the engine head to too much heat. Engine overheating can bring too much stress to the engine head, which weakens the metal. The engine head will eventually crack when the metal has become weak.
Not all cracks are visible outside the engine. The most common cracks on the engine head happen between the valves. These areas have small clearances, and the smaller clearance makes them more vulnerable to cracking once the pressure and heat get too high.
How do you know if an engine head is left or right?
The left side of the engine is on the same side of the vehicle as the driver's seat. Conversely, the right side of the engine is on the same side of the vehicle as the front passenger's seat.
But if the engine’s position is facing one side instead of the front, like in most FWD vehicles, you determine the left and right differently. The side closer to the radiator is the left side, while the side closer to the firewall is the right side.
The firewall is the panel that separates the engine compartment and the passenger cabin. Its primary purpose is to prevent the spread of fire from the engine bay to the passenger cabin should a fire breaks out.
Some V6 and V8 engines have interchangeable left and right engine heads, but not all. The engine head of regular engines does not match even if they look the same on the outside. The only time the engine heads will be a match is if they are engine heads from the same model of engine.
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