Final answer:
The piston and crankshaft are the two major engine components that work together to change the reciprocating motion of the pistons into a rotary motion.
Step-by-step explanation:
In a four-stroke internal combustion gasoline engine, the two major engine components that work together to change the reciprocating motion of the pistons into a rotary motion are the piston and the crankshaft.
The piston moves up and down in the cylinder as the combustion process takes place. This reciprocating motion is then converted into a rotary motion by the crankshaft, which is connected to the piston through a connecting rod.
As the piston moves up and down, it transfers its linear motion to the crankshaft, which rotates as a result. This rotary motion is then used to power other components of the engine, such as the transmission or the wheels of a vehicle.