[mr48chev]

Well 60 years of working on cars and trucks an 70 years of reasonably well understanding what the older guys were saying about what was going on on a car or truck and that thing about the air recirculating back through the radiator is a totally new one on me. I'm not saying that it isn't posible but the likelyhood is so low it can't be measured. For that to happen you would have to have the routes that air normally flows out of the engine compartment blocked off so no air could flow out.

The shroud does make it so the fan pulls air through the whole radiator rather than just the circle behind the fan and that is what it is designed to do. That is why all of us with mechanical fans and no shroud normally see the temp go up when we are at an idle or moving slow because air is only being pulled through that circle in front of the fan and with those ricky racer blades I had on mine that wasn't much air. Hit 25 and you could watch the gauge go down but I have 120 louvers in the hood to help air flow.