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Understanding The SOHC And DOHC Engine Layouts

It’s important to understand your car’s engine, you don’t have to be a technician to know this, matter of fact this knowledge can help save you unnecessary costs. Many vehicles today have specific engine layouts based on the manufacturer’s goals in terms of fuel efficiency, performance and engine size. There are broadly two engine layouts used in vehicles namely, Single Over Head Cam (SOHC) layout and Double Over Head Cam (DOHC) layout. Each layout has it’s advantages and disadvantages. We will be looking at how these layouts affects the vehicle’s performance and which type of engine layout is more preferred by drivers and manufacturers alike.


SOHC means there is a single camshaft operating both the intake and exhaust valves. This mean that the engine head can be smaller, lighter and have more fuel economy, but they aren’t as efficient as DOHC.  The SOHC engine is more affordable in terms of cost than the DOHC because of it’s single rotating cylindrical rod that regulates the intake and the exit of fuel as against the DOHC which have distinctive setup for both the incoming and outgoing of fuel.

DOHC means there are two camshafts, one operating the intake valves and one for the exhaust valves. These allow for more accurate timing, and therefore create more power and work more efficiently but not particularly as fuel efficient has the SOHC. The downside is they are slightly heavier than SOHC and take up more space within the engine.

However the extra power and efficiency of DOHC heavily outweighs the added weight and larger heads, and therefore are preferred over SOHC.

About Nonso Okafor

I've worked as a technical support representative in major auto centers in Nigeria for more than twenty years. I have dealt with a variety of problems in my capacity as a customer service representative and auto diagnostics expert. I'm committed to assisting people in properly maintaining their automobiles and in appreciating this magnificent innovation known as an automobile.

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