Heating Air Conditioner Repair
OHV, or Overhead Valve
This means that the valves which allow the air-fuel mixture to enter and exit the cylinders are located above the camshaft which is in the engine block. The camshaft activates pushrods which move up and down to open and close valves in the engine block.
Although OHV engines are also known as pushrod engines, they can produce a lot of torque at low engine speeds, but cannot run at the same high engine speeds that overhead-camshaft engines.
For many years, they were used extensively by domestic manufacturers. Today, OHV engines like the GM's 5.3 and 6.2 liters V-8s and the Stellantis 5.7 and 6.2 liter V-8s are used mainly for large pickup trucks and SUVs. However, performance models such as the Dodge Challenger SRT and Chevrolet Corvette also use them.
SOHC or Single Overhead Camshaft
An OHC engine has the camshaft in the cylinder head above the valves. The camshaft works directly on the valves and rocker arms that open or close the valves. One camshaft can open and close both the intake and exhaust valves in an OHC engine.
SOHC engines can generally run at higher speeds than OHV engines. A smaller SOHC engine can produce more horsepower than an OHV engine, and can often provide better fuel economy. However, SOHC engines don't generally produce as much torque at low speeds as OHV engines.
DOHC or Dual Overhead Camshaft
DOHC engines are today's dominant type. They are efficient and produce the most horsepower per liter. Dual camshafts operate the intake and exhaust valves. A V-type horizontally opposed engine will have two camshafts for each cylinder bank, making it four total.
DOHC engines allow for four valves per piston instead of two. This improves airflow, power, and efficiency. DOHC engines have more parts and are therefore more costly to make.
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