Originally Posted by 08LegndShelbyGT

here is the technical way of looking at it.

Cowl induction has been used since the early days of Grand Prix racing in 1910. This method is a proven, if somewhat antiquated, way to make horsepower. Cowl induction hoods use a backward-facing scoop in the hood to draw in some of the cool, high-pressure air that collects on the windshield at speed. Though a properly engineered cowl-induction system looks good and works well, there are a number of options available on the market that don't carry many of this system's drawbacks.
Power Functions
As a car punches through the stagnant air at high speed, there are a number of areas that tend to accumulate high-pressure pockets. The front bumper, grille, headlights, windshield and wheel-well are the most common areas.

Since engines make more power with cool outside air than the hot ambient air found in the engine bay, it seems logical to tap these high-pressure pockets to feed air to the engine. In addition to lowering air temperature, increasing the air pressure around an intake artificially crams more air into the engine than the static air could, which is similar to how a supercharger functions.
Other Functions
Cowl induction hoods are used for a number of other reasons as well, prime amongst which are intake clearance and cooling. Since many performance intakes (particularly those found on carbeurated vehicles) are taller than stock, there may not be enough room under the hood to fit an air cleaner.

The second ancillary function of cowl hoods has to do with cooling. Though these hoods draw in cool air while at speed, when idling or cruising at low speed they go from intake to exhaust. Since performance cars tend to produce excess heat when idling, the ability to vent hot air from the engine bay may be the difference between a fun night out and a melted motor.

just a little article i found on cowls...so they do work.

Originally Posted by deekum1627

i got the 4 inch to me the 2.5 isnt big enough for me. i think the 3 inch would be perfect cause that is what i had on my bronco, but they dont make a 3 inch. as for cooling i dont think it will make a diff if u get a 4 inch or a 2.5 inch. go with what you like best

Originally Posted by dopeboifrsh12

Migh not be on topic but wouldn't a shaker system do more than a new hood?

Originally Posted by Riptide

My concern with the cowl is that I don't particularly care for the look of the 4" models. The 2.5" looks better to me but I wonder if it is to small to make any impact on cooling the engine bay.

The cervinis "heat extractor" hood looks like it might be functional but it really does about -0- for the styling of the car.

Ideally I would like something that has an impact on engine compartment heat and yet looks cool at the same time. Hence my question regarding the cowls.