Here's how it works:
1. Camshaft: This rotating shaft has lobes (bumps) that are shaped to match the profile of the valve lifters.
2. Valve Lifters: These are small cylindrical pieces that ride on the camshaft lobes.
3. Pushrods (in overhead valve engines): These rods connect the valve lifters to the rocker arms.
4. Rocker Arms: These pivoting arms are connected to the pushrods and transfer the motion to the valve stem.
5. Valve Stem: This stem connects the valve head to the valve spring.
6. Valve Spring: This spring keeps the valve closed when not actuated by the camshaft.
The Process:
As the camshaft rotates, the lobes push up on the valve lifters. This motion is transferred through the pushrods (if present) and rocker arms to the valve stem, lifting the valve open. When the lobe rotates past the lifter, the valve spring pulls the valve back closed.
Different Engine Types:
* Overhead Valve (OHV) engines: These engines have the camshaft located in the engine block, with pushrods connecting the camshaft to the rocker arms.
* Overhead Cam (OHC) engines: These engines have the camshaft located in the cylinder head, directly above the valves, eliminating the need for pushrods.
In both engine types, the camshaft is the primary component responsible for opening and closing the valves in a four-stroke engine.
