Junior AACA







What is inside an Automobile Engine?

Overall there is 100s of parts but there is only really only 7 key parts that exist in almost every engine. They are:




connecting rods

exhaust and intake valves and springs

timing gears or chains

and, an oil pump

The pistons are round metal or aluminum parts that slide up and down in the cylinders of an engine. There is a connecting rod connected to the pistons. The other end of the connecting rod is attached to the Crankshaft.

The crankshaft is a strong steel part that each piston is connected to. It turns (rotates) and because of the design or shape of the crankshaft where the piston connects to it, the pistons move up and down (see drawing B).

The camshaft is what opens and closes the intake and exhaust valves

Intake and exhaust valves are pushed open and close because they ride on the revolving camshaft that has a high or pointed areas and low spots on it. These are called cam lobes. The valve rises when the high spot on the cam passes under the valve. It is lifted against a valve spring resistance and when the high point of the cam move to the low part of the cam the valve spring forces the valve to close.

In this engine and most engines there are 2 valves which have springs for each piston and cylinder. One is called the intake valve and is where the mixture of gas and air from the carburetor is pulled or sucked into the cylinder, after the gas is in the cylinder the intake valve closes and the piston rises to the top compressing the gas to allow the gas to be ignited from the spark plug, the explosion force the piston down to turn the crankshaft and move the car. The second valve is the exhaust valve. Its purpose is to open up after the gas in the cylinder has exploded and needs to leave the cylinder. The burned gases from the engine cylinder leave the engine and go through the exhaust and muffler system to outside air.


valve without spring