There are two types of valves in an engine .
Do you know what they are ??
If you said INTAKE and
EXHAUST you were right.
OK , I'll tell you what each one does and
show you how each one works in the pictures below.
| Notice how the intake valve is open. It opens when the piston
is going down sucking the air and gas mixture into the cylinder. The Intake
Valve closes when the piston reaches the bottom and starts back in the up
ward stroke or called the Compression stroke. When the intake valve closes it makes a air tight chamber.(some times called the COMBUSTION CHAMBER) |
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| After the spark plug ignites the gas and forces the piston downward . You have burnt gases in the chamber and the engine has to get rid of them. So when the piston starts in the upward motion the Exhaust valve opens so the burnt gases can escape out through the Exhaust valve and out through the muffler and tail pipe of the car. |  |
| The camshaft is timed with the crankshaft so that it turns at half the speed
of the crankshaft. It's purpose is to open the valves when it's there turn to open
at the proper timed. The camshaft is as long as the engine and that's because it
has to open valves the lenght of the engine. To do this it has bumps ( called
lobes ) on it for every valve it has to open. (
See fig 8.)
| 
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| As it turns the bumps push up a thing called a lifter which push up a push rod and then the push rod pushes a rocker arm and the rocker arm pushes down the valve. |  |
| The push rod is a round tube about 3/8 of an inch and about 10 to 12 inches long.(See fig 9.) |  Fig 9. |
| The Rocker arm is bolted in some manner to the top of the head
.When the push rod pushes up one end the other end of the rocker arm pushes
down the valve. (See fig 10.) |
Fig 10 |