Quote Originally Posted by joeybsyc
... if my fan is low in the rad (without a waterpump riser) and i put in a walker plastic shroud with the hold cut out low for the fan, leaving the upper portion covered by the shroud, will it help or hurt the amount of air pulled through the rad at idle? .
For any given arrangement, the fan is going to pull the amount of air it's gonna pull (don't you just love profundities?). So neither the fan nor shroud cares whether the hole is at the top or the bottom as far as amount of air flow. The fan shape/design will have more to do with that than location (in this type application). One plausible argument for having it in the upper half rather than lower is that the hottest air will have the shortest path of exit. That said, even with the fan down low pulling through a shroud is better than no shroud for the reasons stated in the above entries.

Now, the type of flex fan you've got there isn't known for being very effective. For a mechanical fan I prefer the type Deuce has in the picture above. If for no other reason, rarely if ever do you see an OEM application overheat. Which fan did they use? The funky little flex fan, or the modest pitched steel fan like Deuce's? (which also has some flex, just not as much).