#1 Poppet Valve
It is also known as a mushroom valve because of its shape. It is used to control the timing and quantity of gas flow into an engine. This is the most widely used valve in an automobile engine. The poppet valve is given the name because of its motion of popping up and down.
It consists of a head and a stem. The valve face usually with an angle of 30° to 45° is ground perfectly, since it has to match with the valve seat for perfect sealing.
The stem has a spring retainer lock groove and its end is in contact with the cam for up & down movements of a valve. In exhaust, a pressure differential helps to seal the valve. In intake valves, the pressure differential helps open them.
#2 Sleeve Valve
The sleeve valve as the name implies is a tube or sleeve that fits between the piston and the cylinder wall in the cylinder of an internal combustion engine, where it rotates/slides.
Ports on the side of the sleeves come into alignment with the cylinder’s inlet and exhaust ports at the appropriate stages in the engine’s cycle.
The inner surface of the sleeve forms the inner cylinder barrel in which the piston slides. The sleeve is in continuous motion allowing and driving out the gases by virtue of the periodic coincidence of port cut in the sleeve with ports formed through the main cylinder casting.
#3 Rotary Valve
There are many types of rotary valves. The figure shows the disc-type rotary valve. It consists of a rotating disc that has a port. While rotating, it communicates alternately with the inlet and exhaust manifolds.
#4 Reed Valve
These are a type of check valve that opens and close the flow of fluid in the same direction under varying pressure on each face. It is consists of a mechanical bar hinged at one end that covers the passage and allows air or charge to flow in only one direction.
This valve is placed such that the suction pressure opens the inlet valve and closes the exhaust valve. And the exhaust pressure closes the inlet valve and opens the exhaust valve. These are usually installed in two-stroke engines.