Definition

• A cam is a cylindrical piece of metal that fits around the camshaft like a sleeve and has one jutting side that tapers off to a point. A camshaft is a shaft that bears a series of cams. These cams have a hole in the middle through which the camshaft fits. When a camshaft rotates, so do the cams.
  
  

Valves

• Sitting on top of each cam is a part called a poppet valve. The rotary motion of the cams cause the irregular shapes to spin. When the jutting part of the cam comes into contact with the valve, the motion is imparted to the valve, and it is lifted up.
  
  

Crankshaft

• The camshaft is connected to the crankshaft by a chain or timing belt. The rotation of the crankshaft does two things: it causes the camshaft to spin, but it also causes the piston to pump up and down. Because all of these parts are linked to the rotation of the crankshaft, the cams are timed to the motion of the piston.
  
  

Fuel

• The purpose of the camshaft is to control the flow of fuel in and out of the cylinder through the valves. There are two cams per piston: one to let fuel in and one to let fuel out. One cam is rotating slightly behind the other, so that each valve can be perfectly timed to do its job.
  
  

Strokes

• There are four different strokes in a single cycle. During the induction stroke, one cam lifts the inlet valve up so that the mix of fuel and air can flood into the cylinder. The inlet valve closes and the piston compresses the mix. This is known as the compression stroke. A timed spark ignites the mix during the power stroke. And the exhaust stroke expels the burnt gases through the cam-driven exhaust valve. The cycle continues to repeat for as long as the engine is running.