OHV vs OHC
The term “OHV” stands for “overhead valve” and “OHC” stands for “overhead camshaft.” These terms actually describe the cylinder head layout of a piston engine.
OHV
An overhead valve (OHV) cylinder head configuration is used in today’s modern-day engines where valves are arranged over the cylinders. It is different from the older engines where valves were actually installed beside the cylinders. OHV engines have the camshaft below the cylinder head which uses lifters, rocker arms, and push rods to actuate the valves in the cylinder head.
The other characteristic of this type of cylinder head configuration is that it is more compact than the OHC configuration. However, it is less efficient as compared to the OHC configuration due to the increased weight of the valve train.
OHC
An OHC type of cylinder head configuration does not have the weight of push rods and lifters to tackle. The total mass of the push rods and lifters is around 15 to 17 per cent of the total mass of the valve train of an engine. Therefore, it provides a big difference to the output of the engine. More power is transferred to the crankshaft in an OHC configuration. In other words, the power from an OHC configured engine is better than the OHV configured engine.
OHC cylinder head configurations are of two types; one is an SOHC (single overhead camshaft) and another is the DOHC (double overhead camshaft). In an SOHC, one camshaft is installed in each cylinder head while in a DOHC, two camshafts are installed in each cylinder head. An SOHC generally uses two valves per cylinder while a DOHC uses four valves per cylinder.
Summary:
- “OHV” means “overhead valve” and “OHC” means “overhead camshaft” configuration of the cylinder head.
- The OHV is a more compact design but less efficient while the power output is higher as compared to an OHC.
- An OHC configuration does not have lifters and push rods to deal with and, therefore, the total mass of the valve train is less. This makes it more powerful than an OHV configuration.
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The Riley “High-Cam” Hemi provides many of the benefits of both: Gear driven cams ( no belts or chains) direct drive ( no tensioners) very short push rods (low inertia) compact overall size, no rockers) no lubrication problems and ( important this, some 70 years ago) no re-timing every time the head came off!
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Your summary says “The OHV …… while the power output is higher as compared to an OHC.“ while “An OHC configuration does not have lifters and push rods …….This makes it more powerful than an OHV configuration.”
That’s contradicting. Which one is really powerful?
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