1. Valve Train (Camshaft, Rocker arm, Pushrods) By: Hewett Sze
Objective:
To give an overview of how these components function in an engine and how their configurations affect engine performance.

2. Valve Train
The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft.

3. Camshaft http://static.howstuffworks.com/gif/camshaft-ch.jpg

4. Cams continued…
The camshaft uses lobes (called cams) that push against the valves to open them as the camshaft rotates
Springs on the valves return them to their closed position

6. A pictorial representation of intake and exhaust valves

7. Rocker Arm
Works as an intermediary between the camshaft and the valves
Camshaft cam pushes up on the rocker arm (via a push rods) which in turn pushes down on the valves

8. Piston Engines
Some older engine models placed the camshaft below the pistons
Pushrods actuated rocker arms above the cylinder head to actuate the valves.
Lifters or tappets reside in the engine block between the camshaft and pushrods.

9. Overhead Cam Systems
Place the camshaft above the cylinder heads and drive the valves or lifters directly instead of using pushrods.
This arrangement is more complex, and relies on a timing belt or chain, but allows for greater valvetrain flexibility.

10. Single Overhead Cam (SOHC)
One Camshaft is located above the valves
The one camshaft controls both the inlet and exhaust valves

11. Dual Overhead Cam (DOHC)
Two camshafts for each bank of cylinders
DOHC engines have separate camshafts for inlet valves and exhaust valves
DOHC allow for more valves in each cylinder than SOHC
More valves allow for greater intake and exhaust flow and greater engine power

12. Conclusion
3 types of engines that use different valve train configurations are Piston Engines, Single Overhead Camshaft Engines, and Dual Overhead Camshaft Engines
Modern Engines use overhead camshaft configurations

13. Sources http://www2.gsu.edu/~bioasx/engine.gif