Please check out the question I posted here:
http://www.s197forum.com/forum/showthread.php?p=322820#post322820
http://www.s197forum.com/forum/showthread.php?p=322820#post322820
mine spins in either direction. Apparently built into the stock pulley is a clutch that only allows it to go one way. We dont have that in 8 rib kits
The only thing I could find was that it is relative to the cooling charecteristics which in turn prevents over heating.Also by reversing the rotation current flow is also reversed. This doesn"t mean that Polarity is reversed, just the direction in which it flows. Diodes are made for current to flow in one direction. Kind of like the same principal that a water pump works on, the impeller will move more water, faster, and more effectively cool, opposed to when it spins in the opposite direction. Hope this helps. Also changing operating range rpm's will also affect output.