What do DOHC, SOHC and OHV stand for?


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Automakers often throw around terms that may seem like alphabet soup to some, including engine descriptors like DOHC, SOHC, and OHV. These engine acronyms can be confusing. This is what they stand for:

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OHV or overhead valve

This means that the valves that open and close to let the air-fuel mixture in and out of the cylinders are located above the camshaft, which is located in the engine block. The camshaft activates pushrods that move up and down to operate rocker arms that open and close the valves in the cylinder head.

OHV engines, also called push rod engines, can produce a lot of torque at low engine speeds, but not at the same high engine speeds as overhead camshaft motors.

They were widely used by local manufacturers for years. Today OHV engines like the 5.3 and 6.2 liter V-8 from GM and the Stellantis 5.7- and 6.2-liter V-8s are primarily used in large pickups and SUVs, although they are also used by the Chevrolet Corvette and performance models like the Dodge Challenger SRT.

SOHC or Single Overhead Camshaft

In an OHC engine, the camshaft is in the cylinder head above the valves, and the camshaft acts directly on the valves or on rocker arms that open and close the valves. In a single OHC engine, a camshaft opens and closes both the intake and exhaust valves.

SOHC engines can generally run at higher speeds than OHV engines, so a smaller SOHC engine can achieve at least as much power as a larger OHV engine and often lower fuel consumption. One disadvantage is that SOHC engines generally don’t produce as much torque at low speeds as OHV engines.

DOHC or Dual Overhead Camshaft

DOHC engines are the dominant type today because they are the most efficient and can produce the most horsepower for their size. With two camshafts, one actuates the intake valves and the other actuates the exhaust valves. In a V-type or horizontally opposed engine, each cylinder bank has two camshafts, making a total of four.

DOHC designs also allow the use of four valves per cylinder instead of two, which improves airflow and increases performance and efficiency. A disadvantage of DOHC engines is that they have more parts and are more expensive to manufacture.

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