Overhead Valve (OHV) Engine:
* Valve location: The valves are located in the cylinder head, above the pistons.
* Camshaft location: The camshaft is located in the engine block, below the cylinder head.
* Mechanism: The camshaft operates the valves through pushrods and rocker arms.
Cam Engine:
* This term is more general and simply refers to any engine that uses a camshaft to operate the valves.
* Valve location: Can be overhead (OHV), overhead camshaft (OHC), or even in the block (as in some older designs).
In essence, all overhead valve engines are cam engines, but not all cam engines are overhead valve engines.
Here's a table summarizing the key points:
| Feature | Overhead Valve (OHV) | Cam Engine |
|---|---|---|
| Valve Location | Overhead | Can be overhead, overhead camshaft, or in the block |
| Camshaft Location | In the engine block | Can be in the block or in the cylinder head |
| Mechanism | Pushrods and rocker arms | Various mechanisms, including pushrods, timing belts/chains, and direct actuation |
Why the distinction is important:
* Design and complexity: OHV engines tend to be simpler and less expensive to build, while OHC engines can offer better performance and fuel efficiency due to their more direct valve actuation.
* Terminology: While "cam engine" is more general, "overhead valve" specifically implies the arrangement where the valves are located in the cylinder head, above the pistons, and the camshaft is in the block.
In everyday conversation, "cam engine" is often used as a shorthand for "overhead camshaft engine". However, being aware of the technical difference is helpful for understanding engine design and terminology.
