Quote Originally Posted by charles_h View Post
It's my understanding that the major reason for going in through the "in" barb is related to air and bleeding.
Ture, that's part of it. But an even greater reason is that the central inlet is positioned in the center of the block (duh!), which is right over the core under the IHS. By using the normal inlet the water is directed straight at the core, giving the best heat absorbtion. I don't know how much of a temp difference we're talking, i'm not sure it has been tested, but i know the theory is right.