DOHC vs. SOHC – Which Engine is Better?

Understanding the basic differences between the various camshaft engines for your vehicle is super important if you’re planning to make the most of what you have.

Not only will this allow you to have a better drive, choosing the right engine literally means you’re investing in your future. This is because of its effect on fuel efficiency, performance, comfort level, and so many other things that people often take for granted.

In this segment, we’ll be going over the main two types, DOHC and SOHC, and present a case for both. However, before we begin, let’s go over basic things and then expand on them further.


What is a camshaft?


You might have noticed above that DOHC and SOHC are categorized as camshaft engines for your vehicle. But what exactly is a camshaft?

A camshaft is a critical part of your engine that enables valves to open. Furthermore, it is also responsible for the input of the fuel and the expulsion of the exhaust fumes. Made up of several parts, a good camshaft is absolutely essential when it comes to regulating your vehicle’s performance.

Now that we’ve covered the first base let’s dive right into the SOHC and DOHC and their main differences.

What is DOHC?


The Dual Overhead Cam or the Double Overhead Cam, better known as the DOHC, is the engine that recruits two camshafts. This is evident in the name as well. However, it only has one header.

Furthermore, a DOHC also has four valves with different camshafts per cylinder, each operating a different task, such as opening the exhaust valves or the intake valves.

All these cams work in conjunction and are normally tied together by a short chain.

What is SOHC?


As the name implies, the Single Overhead Cam, better known as SOHC, only has a single camshaft that can be located on top of the engine head.

This singular head is responsible for all tasks, which include the regulation of the intake and exhaust valves.
Addressing the main differences

Now, we’ll go over the main differences between the two types of engines based on tangible outputs.

The main purpose of this is to literally distinguish their main features, which will allow you to make a better call for yourself in the future. Plus, if you feel like you’re missing out, this segment might actually help you solidify your decision to get the upgrade you want.

Without further ado, here are the main differences between SOHC and DOHC!

Noise reduction

engine noise
engine noise

The first thing that we’ll address is the most obvious one. Generally speaking, if you’re just starting out or want to see the difference right away, this is the first thing you’ll notice.

When it comes to noise reduction, the best bet is opting for a DOHC engine.

This is because a DOHC engine recruits multiple valves that are individually responsible for taking care of the intake and exhaust. This is, of course, better than having one valve control everything, just as the SOHC does.

The main thing that this results in is the higher efficiency of the engine and less friction. Put it this way: you can have one man do two jobs, or have two men do the two jobs. Which would you think is a better option?

Just like this, DOHC definitely takes the round with ease. However, this alone shouldn’t be enough incentive to make the final call for yourself. Keep reading!

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Valve timing

Valve timing
Valve timing

The crux of all vehicles is the internal combustion engine, which is responsible for two internal processes that control your vehicle’s performance – the ignition and the fuel-air mixture.

The latter is directly responsible for moving the pitons, whereas the former requires the accurate timing of the fuel injection and the effective ejection of exhaust gases.

The important thing to remember here is that the camshaft will influence how the intake and the outtake gases perform. On top of that, if the timing is on point, so will the horsepower. When it comes to DOHC and SOHC, there are both pros and cons.

A DOHC is a better performance since it has better and more effective configurations with the valves, allowing for better control of the intake and outtake gases. However, the main downside is that it will cost you more.

On top of that, an enhanced DOHC engine also means that your car will be heavier. If you’re sporting a lighter vehicle or want to keep it that way, this would be counter-intuitive. So you’ll have to give it much thought before pulling the metaphorical plug.

On the other hand, we have SOHC engines. They’ve been around for quite some time, and all earlier models have them. However, they have the ultimate disadvantage of providing less control over the valve timing.

Nonetheless, they are lighter and still retain functionality. So what will it be?

Most engines these days already come fitted with DOHC engines, so you won’t have to worry about an upgrade. However, if you’re planning to go old-school, then you’ll definitely need to get your hands dirty.

Fuel efficiency

Fuel efficiency
Fuel efficiency

Fuel efficiency is a great factor to consider if you’re planning on experimenting a little. Since most earlier vehicles came imbedded with the SOHC engine, a gradual shift to DOHC and the influx of modern engines saw a rise in fuel power and efficiency.

Here’s the science behind this.

With a DOHC head, you’ll, of course, have two sets of valves. Along with providing an enhanced control, this also means that your engine is better equipped to handle fuel expenditure.

However, there are a few other things that you’ll need to keep in mind, as well. Your fuel efficiency will also depend on the make f your car, how old it is, your current expertise level, and the gear transmission.

It’s foolish to assume that just an upgrade from a SOHC to a DOHC will do the job. However, there will be an improvement in inefficiency. The only downside? Your vehicle will be heavier than before.

This means that again if you’re sporting a muscle car or want to be lightweight, this is a little counterintuitive.

On the other hand, the SOHC engine isn’t as fuel-efficient as its successor. This is, of course, because it employs fewer parts and fundamentals to get the same job done.

What results is a messier job done that isn’t handled as well as it should be.



When it comes to performance, the DOHC and SOHC both tie due to their benefits on polar ends.

First things first, the SOHC engine, with its 16 valves, produces excellent torque even if compared to DOHC with the same amount of valves. The main reason for this is its lightweight.

As mentioned countless times above, the DOHC suffers here due to its bulky frame. However, that does have a silver lining. This enables it to produce more horsepower at higher speeds.

Another swift comparison is of the low-end torque and the top-end torque. For the former, SOHC is the undisputed champion, whereas DOHC can better handle top-end torques.

Nonetheless, even with all this in mind, the gradual shift towards better gear and technology has favored DOHC engines. Recent studies and experiments have shown that at low RPM, the number of valves didn’t really influence the performance.

What really mattered was shifting to the next gear. And for that, the number of valves most definitely mattered.
In the end, however, everything trickled down to the weight. Not everyone wants a heavy engine when a lighter one can do the job as well.

Spark plugs

Spark plugs
Spark plugs

Last but not least, one difference that you’ll notice when it comes to this small comparison is that with the DOHC, you’ll be better able to locate the spark plugs.

When it comes to the SOHC, you’ll notice that the SOHC will be responsible for handling both the intake and the outtake with the same engine based. For this reason, it has to be strategically placed in the middle of the combustion chamber.

Hence, the spark plugs need to be placed where they can be accommodated easily, as opposed to being placed where they can perform well.

This is why their overall performance is massively hindered when it comes to SOHC.

With a DOHC, however, you can easily place the spark plug in the center of the combustion engine. Their optimal placement means that you can have the best performance.

Furthermore, its placement also allows for easy check-ups and maintenance checks. In the long run, this is a great feature to have.

Final Thoughts

With the right choice, you can make sure that your driving experience is unparalleled and worth of envy.
We hope that the above segment helped you get perspective about what you want and that you’re now better equipped to make the right call. If you have any feedback or suggestion or feel that we missed something about the content, do share them in the comment section below!

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