What is the Purpose of a Cylinder Head in a Diesel Engine?

Today were going to go over a little bit about cylinder heads. Before diving head first into the cylinder head market, its important to have an understanding of what youre working with. Heres what we think you should know!



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Identifying the Components of a Cylinder Head


First, before we talk about how each part of the cylinder head works, we should mention what they all are. The cylinder head is going to have your intake valves, your exhaust valves, and it's also going to house your fuel injector down through the center. The head sits on top of your engine and is essentially the control center for your combustion chamber. 


Weve highlighted the parts on our cut-away engine so you can have a look at the different components inside.


Intake Valve:

The highlighted valves in the image below are your intake valves:

cylinder head intake valves diagram | Highway & Heavy Parts


Exhaust Valve:

Below are your exhaust valves:


cylinder head highlighted exhaust valves diagram | Highway & Heavy Parts


Fuel Injector Bore:

You can see the highlighted yellow bores are going to be your fuel injector bores:


cylinder head highlighted fuel injector bores diagram | Highway & Heavy Parts


With the components working together to allow for combustion, the head is essential for controlling the functions of the combustion chamber. Let's take a look at the individual components a little more closely:


cylinder head intake portcylinder head intake valves diagram | Highway & Heavy Parts


Heres a look at the intake port of the head. Essentially when your engine is running, it's going to be taking clean fresh air through the intake port and into the combustion chamber. At that point, your combustion process is about ready to happen.

If you suspect issues with your valves, check out our article on valve failure analysis!


cylinder head fuel injectorcylinder head intake valves diagram | Highway & Heavy Parts


The highlighted portion of the screenshot above is the fuel injector. Your injector is going to inject fuel into the cylinder, while the piston is traveling upward creating pressure. When the explosion from this happens, it's going to create your exhaust. 


If youre interested in the function of fuel injectors, weve also written a blog post explaining that!


cylinder head exhaust valvescylinder head intake valves diagram | Highway & Heavy Parts


The next step of combustion is getting rid of exhaust. The rocker lever is going to then open the exhaust valves and that spent air fuel mixture is going to be let out of the exhaust port. This happens at the backside of the head. 

If youre considering purchasing a cylinder head, check out our previous buying guide article!

Taking a Look at Cylinder Head Fuel Injectors


cylinder head fuel portscylinder head intake valves diagram | Highway & Heavy Parts


The cylinder head were looking at today has fuel ports that run through it, so the fuel runs from end to end of this head.


These fuel ports are running through each injector port, feeding the injectors with the fuel they need for the combustion process. It also has a return port so any of that unused fuel from the injection process goes right back into the tank, giving it an opportunity to cool off.


If your injectors arent working properly, and combustion isnt as effective as it could be, your fuel economy will take a hit. Learning the common signs of fuel injector failure could save you in the long run.


The Basics of Different Cylinder Heads


cummins detroit diesel and caterpillar cylinder headscylinder head intake valves diagram | Highway & Heavy Parts


Weve covered some of the functions, now lets take a look at the basics of how cylinder heads can be different. 


The particular cylinder head we looked at today is off of a Cummins N14. While the N14 uses 3 cylinder heads on that engine, some engines, like the Detroit Series 60 or Caterpillar 3406E/C15, are going to have 1 single long cylinder head. 


When working with the N14, one guy should be able to handle it. The Caterpillar or Detroit are a lot to handle, so you'll probably want to use a hoist on those. If youre curious on whether or not you should replace your head, heres some useful information detailing the signs its time for replacement.

So if you're in need of a cylinder head, rebuild kit, or anything else you need for your engine overhaul, call our ASE certified techs at 844-304-7688. You can also request a quote online!

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