Sohc And Dohc Engines

SOHC vs DOHC, which is the better deal?

While reading about a motorcycle’s specifications, you might have encountered some technical acronyms like SOHC, DOHC, etc. So, if you are having a hard time learning about these mechanical terms, you are at the right place. Here, we have SOHC vs DOHC explained in brief.

Before comparing SOHC and DOHC and getting into technical details, let’s try to understand the use of a camshaft. Camshaft, placed inside an internal combustion motor, is a rotating barrel-shaped bar with various oval flaps which project from it. With each rotation, the differently situated projections first push the intake valve to permit air inside the cylinder to blend in with the fuel and combust. Afterwards, the exhaust valve for the resultant gases is released.

In modern versions of bike motors, valve springs give the return force to the valves to pull their shut position once the projection rotates away.  They are important to determine the RPM range of a motor’s power band.

Single overhead cam setup

A SOHC arrangement normally permits 2 or 3 valves for each cylinder setup, where generally, one valve permits air to enter and the other permits gases to release. In any case, a manufacturer’s design ability can permit 4 valves for each cylinder arrangement using SOHC. Such an arrangement takes into consideration more flow of air than 2 valves for each cylinder, as there is a wider region for the air to enter the cylinder and gases to escape from when the valves are open.

SOHC 4 valve engine gives better force towards the low end due to the lesser mass of valvetrain in this specific arrangement. Because of the greater mass of the valvetrain, a DOHC design will deliver lower torque at first with the same number of valves, but the top-end performance will be better. Another advantage of two valves for every chamber arrangement is the lesser number of components used which helps in cutting costs.

The plan will be better for low and mid-range torque as the airflow is quicker at these motor velocities because of a more confined stream. In a SOHC arrangement, the camshaft is typically positioned in the middle, which doesn’t let the sparkle plug have its optimal location.

Dual overhead cam setup

DOHC was launched to improve the volumetric proficiency of an internal combustion motor, the consequence of which is all the more impressive. With this plan, camshafts can be placed farther away from one another. This permits the intake valves to be at a further point from the exhaust valves, which brings about a more direct wind stream through the motor with less impediment.

All in all, a DOHC motor can inhale better and hence produce more torque out of smaller motor displacement. Additionally, it is simpler to execute efficient technologies like Variable Valve Timing in a DOHC motor.

A dual overhead cam or twin-cam engine has two camshafts for each bank of the cylinder head, one each for the inlet valves and exhaust valves.

In this manner, there are two camshafts for a straight motor and a sum of four camshafts for a V motor or a level motor. In some cases, a DOHC V motor is advertised as a quad-cam motor; nonetheless, the extra two camshafts are a provision of the motor’s layout, giving an advantage compared to other DOHC motors. To further complicate the understanding, some SOHC flat twin and V-twin motorcycle engines made by Harley-Davidson, Riley Motors, and Triumph have been advertised with the deceptive term “twin-cam motor”.

In conclusion, a 4 Valve for each chamber SOHC engine with a lighter valvetrain mass will have better performance concerning horsepower yield. In any case, at higher motor paces, a DOHC arrangement with its higher valvetrain mass and numerous valves per chamber will foster higher force and torque.

390 Duke Dohc Engine

390 Duke DOHC Engine


Advantages of DOHC

  • The DOHC has double the number of valves than the SOHC, which permits them to be put in an ideal situation for enhanced performance. In DOHC, there will be no less than four valves or more based upon the make and model. This aids in a better wind stream and hence brings about a smooth and clamour-free ride.
  • Valve timing can be conveniently optimized in DOHC. The timing of valves is an important factor for determining the performance and efficiency of the engine. The latest versions of motors come with variable valve timing innovation to upgrade the activity of valves.
  • SOHC have significantly lesser control in valve timing because of the presence of a single camshaft for both inlet and exhaust valves. While in DOHC, the timings can be better improved as there are disengaged shafts for intake and exhaust valves.
  • It allows a better position of valves, just like the sparkle plug. The valves can be placed at a certain angle for maximum wind flow possible, and the spark plugs can be placed in the middle, resulting in better ignition. This is not possible in the case of SOHC, as the camshaft operating both the valves needs to be placed in the middle.
  • As DOHC has more parts and consequently higher mass, even though the torque is lower, the top-end execution will be vastly improved.

Disadvantages of DOHC

  • The complexity and weight of the engine are higher as compared to cam-in-block plans. Design and manufacturing expenses also exceed the average rate.
  • In contrast to SOHC engine designs, DOHC engines have a more complex chain or belt drive system which in turn decreases the overall performance rate and adds to maintenance expense.
  • DOHC motors have more complex chains and belt drive systems as compared to SOHC engines. This decreases the efficiency and adds to maintenance expenses.
  • DOHC engines tend to be heavier and taller in contrast with SOHC engines.

Advantages of SOHC

  • A single overhead camshaft arrangement represents a simpler and easy-to-use version of the more complex dual overhead cam motor.
  • As the name states, a double overhead cam utilizes two camshafts for each bank of chambers to upgrade valve control resulting in the overall increase of the engine’s weight.
  • Passageways through the motor block and chamber head for pushrods are not needed. The two regions can thus be used for extra or bigger coolant entries, further resulting in cooling effectiveness.
  • Updated cooling, in particular, has a more complex chain or belt drive system, which in turn decreases the overall performance rate and adds to maintenance expense.
  • DOHC motors have more complex chains and belt drive systems as compared to SOHC engines. This decreases the efficiency and adds to maintenance expenses.
  • DOHC engines tend to be heavier and taller in contrast with SOHC in the chamber head regions and can empower higher pressure proportions. This advantages both power yield and fuel efficiency.
  • The single overhead valve design is mechanically friendly and gives the latest motor manufacturers a great deal of efficient performance. Access to all parts of the valve framework, particularly the camshaft, is easier, making the repairs of this particular area cheaper.

Disadvantages of SOHC

  • Engine complexity is heightened. This adds to the plan and assembling costs. There may be a general expansion in motor weight as compared to cam-in-block plans.
  •  Camshaft drives utilizing a chain or a belt can present unwavering quality and maintenance possibilities not normal to cam-in block motors.
  • The motor can become taller and require expanded hood tallness for clearance. Because of the motor size increment, weight may increase as well.
  • Variable valve timing is to a great extent limited to timing changes for both intake and exhaust valves all the while. This is the same planning issue that exists for cam-in-block motors.

SOHC vs DOHC based on several factors


One of the vital contrasts between the SOHC and the DOHC is the way they work. In the SOHC, you will have one camshaft that operates the intake and exhaust valves, while on the other hand, with DOHC, you have two separate camshafts that operate the two valves. This key distinction impacts how the two motors work. The DOHC has the advantage of being more productive and making less noise. The outcome is that you have a smoother ride.

Valve timing

The internal combustion motor works principally by the ignition of the air/fuel combination. The blast is extreme and moves the cylinder vigorously, and the cylinder ring is associated with the driving rod through the interfacing bar. The camshaft has intake and exhaust valves and a need for accurate timing with the driving rod, which is why different crankshaft belts/chains connect the two.

The angle of the camshaft is what impacts the opening and shutting of the intake and exhaust valves. This planning must be accurate. DOHC camshafts have preferable command over valve timing over the SOHC ones. This adaptability makes for more horsepower.

Fuel efficiency

The DOHC delivers more force because of the ideal valve timing. At the point when you have a double arrangement of valves per camshaft, more fuel is delivered to the chambers. This prompts more horsepower at the expense of more fuel.

While the SOHC is showcased to be more eco-friendly than the DOHC, it will rely upon the vehicle plan and the driving abilities of the driver. What you keep up with the vehicle will have similar effects on fuel efficiency.

Maintenance costs

The DOHC has double camshafts, which implies you have more valves. This has an immediate bearing on the maintenance expenses as you have more mobile parts. The SOHC is less complex, making it more efficient. The motor is less expensive than the DOHC.

The utilization of one camshaft implies that in the future, you will encounter lower maintenance costs than the DOHC. The DOHC’s complicated nature implies that you have higher productivity and maintenance costs. In any case, the requirement for new vehicle technology favours the manufacture of the DOHC motors.

Spark plugs

The spark plugs for the DOHC are situated in the middle, and this implies they operate both the exhaust and intake valves. This focusing on the valves brings about better ignition and improves performance. The spark plugs are not centred however placed somewhere else. This makes the SOHC motor less proficient. Read more about Spark Plugs.

Which should I purchase – SOHC or DOHC?

With regards to the DOHC, you can incorporate four valves for each cylinder. Two are utilized as intake valves, and two as exhaust valves. This plan empowers the DOHC to be more productive with the gases in the ignition cylinders. The sparkle plugs are situated in the middle, which makes them more productive in the ignition interaction.

You may also need to consider how much power you want for your vehicle. Because of the fewer possibilities of inertia in the DOHC motors, it means they produce more power than the SOHC engine. If the driving rod moves faster, you experience more torque. Since you have double camshafts, you can adjust how the intake and exhaust valves work. A single DOHC motor can create both low and high rpm.

How can you tell if you have SOHC or DOHC installed in your vehicle?

You can just open the hood of your vehicle and analyze the highest point of the motor. A narrow and tall motor top with an unmistakable mound at the front for the cam drive sprocket will show that a SOHC is concealed underneath.

A wide motor or potentially two-humped top will indicate the presence of a DOHC arrangement. If all else fails, simply search on the internet for the make, model, year, and motor size for your vehicle, which gives you a clear answer to this question.

You can read more about OHC on Wikipedia.


Your choice concerning which to pick will rely upon the potential maintenance costs. SOHC motors are easy to manufacture and use. This means they have fewer motor parts, subsequently making them more reasonable. They are more eco-friendly. But, in case you are searching for power and speed and wouldn’t mind the maintenance expense, you should go with the DOHC motor.

Today, we have more fuel-efficient DOHC motors as car engineers change the motor plan. You will find that most V6 and V8 motors are furnished with DOHC camshafts. At last, what you decide to go with will be based upon your requirements. It will be a factor of your financial plan – what amount you can afford to pay.