1) Reduces parasitic losses due to accessories by putting bigger pulleys on them and turning them slower.
2) Allows you to change the cam timing. Note: The 7a cams are geared together, only one of them is turned directly by the crank, therefore you can only adjust them both together, which probably won't get you anywhere.
3) Same as 1) but uses a smaller crank pulley to do the same thing. Not recommended to be used with 1) because your stuff will turn too slow and not work right.
Also, 1) and 3) free up a little power because they reduce the rotating mass of the engine. I think 3) is probably more effective because of this.
Crankshaft pulley is what drives ur AC/Alternator and the Overdrive pulley, idk if thats just a driive pulley or something to do wiith auto tranny's.
The sprocket drives the camshaft which drives the valves to open and close.
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