Toyota 4age 16v

The cam gear is the gear attached to the camshaft. The camshaft is was opens and closes your exhaust & intake valves (there are more parts involved internally, but this is a basic explanation). The cam gear is connected to a belt, which connects to your crankshaft (among other things). The belt synchronizes the valve timing (opening & closing of the valves) with the appropriate strokes of the crank (intake stroke, compression stroke, power stroke, & exhaust stroke). Basically it makes the intake valves open up at the intake stroke, the exhaust valves open up at the exhaust stroke, etc. This is a VERY basic explanation of how it works. I would recommend checking out this link and looking at the animated image: http://en.wikipedia.org/wiki/Four-stroke_engine
Watch the valves open and close and it's relation to the turns of the crankshaft.

The adjustable cam gears allow you to adjust the valve timing (when the valves open), to make more power. But unless you understand how and why you should adjust the timing, based on specific parts you have and power you're making, you should NEVER touch the timing. There is no exact setting to set the cam gear(s) to, that will work with every engine (1 setting on a 4ag is probably not right for another 4ag). With a stock engine, Toyota already set it to where it makes the most power as well as the best fuel efficiency. Adjustable cam gears are really only for when you have an aftermarket cam(s), or you're going forced induction. Most people buy them simply for looks, and never adjust them or adjust them incorrectly.

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