I just a bought a Flex a Lite fan 1300 Series for my 1962 Thunderbird and I read that on a note -Not for use with serpantine belt drives because the water pump runs in the reverse direction of standard pumps. What does that mean. I bought this fan under the same spec what summit recommended online. It met all the specs engine size and all model and year. I am just worried of hurting my water pump. My main question is what does that side note mean?