Last month's "How It Works" story gave you the basics of the four-stroke cycle, describing the motion of the intake and exhaust valves in relation to the piston moving up and down in the cylinder.

Correctly viewed, a pushrod engine's valvetrain assembly stands at the gateway of improved power. It is not a collection of components only intended to time and provide the correct valve motion.

This installment of Toyota's Engines 101 series takes a closer look at one of the most critical parts of an engine: its valvetrain. The video establishes what parts comprise a valvetrain, looks at ...