Automakers often toss around terms that look like alphabet soup to some, including engine descriptors such as DOHC, SOHC and OHV. These engine acronyms can be confusing. Here is what they stand for:
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OHV or Overhead Valve
It means that the valves, which open and close to let the air-fuel mixture in and out of the cylinders, are above the camshaft, which is 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 pushrod engines, can produce lots of torque at low engine speeds but can’t run at the same high engine speeds as overhead-camshaft engines.
They were widely used by domestic manufacturers for years. Today, OHV engines such as GM’s 5.3- and 6.2-liter V-8s, and the Stellantis 5.7- and 6.2-liter V-8s, are used mainly in large pickup trucks and SUVs, though the Chevrolet Corvette and performance models like the Dodge Challenger SRT also use them.
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. On a single OHC engine, one camshaft opens and closes both the intake and exhaust valves.
SOHC engines generally can run at higher speeds than OHV engines, so a smaller SOHC engine can produce as much or more horsepower than a larger OHV engine and often better fuel economy. 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 dual camshafts, one operates the intake valves and the other the exhaust valves. On a V-type, or horizontally opposed engine, each cylinder bank will have two camshafts, so there’s four total.
DOHC designs also allow using four valves per cylinder instead of two, which improves air flow and increases power and efficiency. A downside of DOHC engines is that they have more parts and are more expensive to manufacture.
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