SOHC vs. DOHC – Which Engine is better?

SOHC or DOHC- The confusion may spin your head. But, before moving forward and clearing your doubts, it should be clear that these engine types have several pros and cons that make them distinctive from one another.

Both SOHC and DOHC have managed to gather the limelight for their superior performance when it comes to engine efficiency. But to help you choose better, we have listed out certain factors that will help you make a better choice when SOHC vs. DOHC is in question.

Definitions Of SOHC And DOHC

Engine technology is improved and updated day by day. DOHC and SOHC are the 2 most popular camshaft engines on the auto market today. To have knowledge about these types of motors, let’s update us:

What is SOHC engine?

SOHC stands for Single Overhead Cam (Only one cam rod operating the intake and exhaust valves). That means there is only one camshaft in the head. Inline engines will have one camshaft. The flat engine and V-engine will have two camshafts, one per cylinder bank.


  • At low speeds, SOHC engines will produce more torque than DOHC engines of the same capacity.
  • The simple structure (just has one cylindrical rod) due to the reduced count of parts, the design complexity and manufacturing cost are comparatively low for SOHC engines so its price will be more affordable
  • Because this engine is quite common on the auto market, it is easy to find a repair place when it breaks down, and the cost of repair and replacement is also much lower.


  • SOHC only allows using 2 valves per cylinder, so the same capacity will give a lower capacity compared to DOHC engines.
  • SOHC engines because the camshaft must be located in the middle of the combustion chamber to drive both the intake/exhaust valves, so the spark plugs are not positioned at the center of the car cylinder. This design is not a logical arrangement that will prevent partly the performance of the SOHC engine.

What is DOHC engine? 

DOHC stands for Dual Overhead Cam or Double Overhead Cam (there are two cams located overhead operating various intake and exhaust valves). That means each header has two camshafts. Hence, an inline engine will contain 2 camshafts as it has only one header. The flat engine and V-engine will contain 4 camshafts as they have two headers. The DOHC engines usually come in 4 valves. One camshaft for the intake valves and the other for the exhaust valves.


  • The DOHC was later introduced to improve volumetric efficiency for an internal combustion engine. 
  • DOHC usually implements a four-valve per cylinder configuration (two valves for intake and others for exhaust), so the same capacity level will give a much larger capacity than the SOHC engine. This configuration has a better valve lift resulting in improved airflow through the combustion chamber. It can create more horsepower out of the smaller displacement. 
  • At high speeds, the maximum torque and power of DOHC are higher than SOHC, making the machine stronger.
  • The location of the spark plug in the middle of the top of the combustion chamber helps the DOHC engine to have better fuel combustion efficiency.
  • DOHC engines also possess the advantage of being able to apply variable valve technology, adjusting the camshaft to optimize the operating mode.


  • High cost because the engine structure is complicated with many details and requires higher technology. When there is damage to repair, it requires meticulousness and skilled mechanics. And of course, the replacement and repair cost will be more expensive than the SOHC engines. 
  • The bulky structure increases the weight of the vehicle, which partly affects the ability to operate, or forces the manufacturer to minimize some details to balance.

SOHC vs. DOHC – Which One Makes For A Better Choice?

Each type has its own features that make it unique and distinctive from the others. Let’s look at the difference between SOHC and DOHC in detail so as to help you make a better choice.

1. Operation

A SOHC is simply a single camshaft regulating both the inlet and the outlet of gases and a DOHC is a double camshaft that has a dedicated setup for inlet and outlet of gases. This further implies that a DOHC has double inlet and exhaust valves as compared to SOHC. Thus, this makes for a cooler engine with an equal distribution of operations, which, in turn, leads to a smooth, noise-free, and effective ride experience.

2. Valve timing

Valves are known to activate the working of the engine. The timing of the intake and the outtake of the gases depends on the shape and the angle of the camshaft. When that breathing process needs to be optimized variable valve timing is required, which in turn, also enhances the maximum horsepower attained. It is known that SOHC designs have less control over valve timing as compared to DOHC, owing to the single camshaft availability, making DOHC more flexible in terms of tuning.

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3. Fuel efficiency

As discussed a DOHC has a double setup of valves per head. This, in turn, implies that more power would be consumed owing to the enhanced control over the valves. And, the more the power more fuel consumption. Thus, when talking in terms of SOHC vs. DOHC fuel efficiency, a SOHC is more fuel efficient. However, it should be known that it is the skills of a driver and the design of the engine that can make a DOHC engine reflect fuel efficiency. You could look for maintenance tips that can help you learn how to manage the engine efficiency well.

Find difference between SOHC vs DOHC
Fuel Efficiency of SOHC and DOHC. (Photo: Kadmy – Fotolia)

4. Price

When the question” What is SOHC” comes to your mind, just know that it has a single rotating cylindrical rod that regulates the intake and the exit of gasses. This calls for affordability over DOHC which has a distinctive setup for both the incoming and outgoing of gasses. A DOHC has double the valves as compared to SOHC, which makes it a less complicated design and thus cheaper than its counterpart.

Theoretically, the SOHC camshaft structure has the upper hand at low rpm, while DOHC has advantages at high rpm. But to compare which engine is more efficient depends on materials and precision when making, so it will depend on your car model and the car design from the auto manufacturer to have the most accurate assessment.

Price difference of SOHC vs. DOHC
SOHC vs. DOHC- Which is reasonable? (Photo: Yahoo Autos)


Having looked at the perspectives of the two engine types, you must have got a clearer perspective on SOHC vs. DOHC. Also, one should know that both SOHC and DOHC have their own advantages and disadvantages, but when it comes to choosing a better option keeping in mind the market trends, it would undoubtedly be DOHC.