Originally Posted by hustler316

Air will get sucked back down into the engine not pulled out, there is a high pressure system that is created by the windshield. Since there is a seal on the back of the hood no air escapes from the rear out and over, instead it goes down and under the car. If you vent the rear with hopes of air escaping it simply will not happen unless you are not moving, then it will in fact escape from the rear. The further forward you move them as long as they are behind the radiator the better your chances of air escaping becomes. The best way to effect cooling of he engine is to get air to flow through the radiator with the least amount of restriction. This includes pressure systems, vent the front so air flows through the radiator and out the hood is the best method for this.