It would, make a huge difference. Without one, the air is not going directly from the fan through the rad, but it is going out the easiest way it can. And that will be in bet\ween the rad and the fan, mostely. So having a shroud will direct the flow of air, forcing it into only one direction... The direction which you want... Through the rad. It makes a huge difference. You can make one out of cardboard if you wanted to, but you *should* have one in place.