Hard to believe, but the pressure at the base of the windshield is higher than at the front of the hood. It swirls around in this area, and you get more air.

 

Hm....I take your word for it even though I still dont get it. The way I see it it's physically harder for the air to whirl around then to drift along the windshield. How is the pressure in the lower windshield formed? Does any cowl hood work? I noticed that you put a cowl hood on your blazer, did it have to be designed specifially for the high pressure to occur? So in a car that doesnt have cowl hood induction, does the air whirl around at the lower windshied?



Thanks,



Mike

 

The cowl induction hood looks COOL!! And it works too!!


Tazz


Rat Rods Rule!

 

Cowl Hoods

Poncho hit it on the nose. There is a tremendous amount of pressure in the cowl area. The "cowl" hoods just like the Camaro's prior to 69 on the race cars found that the design of the hood if it had an opening created a large vacuum and air would flow thru the opening.
Remember the 69 Camaro had an ad out that called the system the Super Scoop. It was reffered to as Air Induction. In 1970 the Chevelle came out with "Cowl Induction" and the name has stuck ever since.
If a regular production car did not have a closed cowl area and weatherstrips under the hood to seal it then you would pick up a ton of stuff and find it in the engine compartment.

 

After I installed mine I hung tape off it and drove, sure enough the tape got sucked into the cowl.

 

Hm I noticed that you put a cowl hood on your blazer, did it have to be designed specifially for the high pressure to occur?

Yeah....gained 400 hp in the old 2.8.........................

No...J/K...........just an experiment with some sheet netal.

 

Hey poncho, what yr model you got. Mines 85 and was thinking about a cowl hood for the 283 that Im puttin in mine. What kind of dimensions you got on the cowl.

 

Mine is an 83...same hood.

I just bent up a piece of sheet metal and pop rivetted it on. It's about 20x40x 2 in high.

 

Hm....I take your word for it even though I still dont get it. The way I see it it's physically harder for the air to whirl around then to drift along the windshield. How is the pressure in the lower windshield formed? Does any cowl hood work? I noticed that you put a cowl hood on your blazer, did it have to be designed specifially for the high pressure to occur? So in a car that doesnt have cowl hood induction, does the air whirl around at the lower windshied?





Mike

It is similar to how an airplane wing works.

 

even the 70 chevelle ss ls6 big block only boasted a few h.p. gain. it was 90 percent hype and a two percent gain in power.

 

http://www.camaro-untoldsecrets.com/articles/rpo_zl2.htm

 

It is similar to how an airplane wing works.

Umm, sorta. An airplane wing uses Bernoulli's Principal to create lift. As the velocity of a fluid increases, its pressure decreases.

A wing, or airfoil, does this by curving the top and using a flat bottom. As the air passes over the top of the wing it accelerates and looses pressure, the air on the bottom of the wing is not accelerating, so it keeps the same pressure. This pressure deferential is what causes lift.

In the case of a cowl, the air builds up at the base of the windshield because it kinda has no where to go right away. At the leading edge of a wing the air is directed to either the top or the bottom. On a car, there is nothing to direct the air quickly enough over the vehicle. So the pressure builds. This can also be described as a form of parasite drag.

I guess this turned into an excuse for me to finally use all that information I leaned in those Aerodynamics classes.

:thumbup:

Chris

 

The cowl induction hood only works past a certain speed. It is of no use at slow speeds. The 69 Z/28 had a solenoid operated flap that sealed the back of the hood. The solenoid was operated by a vacuum switch. When the cowl induction hood was shut off (slow speed) the air was taken from under the hood just like a traditional car. Put your foot in the carb and the cowl hood flap opened, or it was open under highway+ speeds. The iar moving over a hood and meeting the base of the windshield does not know where to go. Some of it spills over the top of the car, but a lot of it builds at the base of the windshield and boils off the sides. The cowl hood was designed to take advantage of this phenomenon.

Vince

 

if you think about it when its raining and the wipers push the water down to the bottom of the windshield it doesn't shootback up the windshield so that would mean hat the wind would have to be swirling to stop the water from going back up the windshield, hope you could make sense of that \

my .02

 

Air goes into the cowl scoop, it does not come out. I made a baffle for mine to let air in and keep water out.
Here is a shot of it in the making.

 

Thanks guys:thumbup: I get it now, yet a forward facing scoop makes more sense to me....
But you cant argue that cowl hoods dont look good.







Mike

 

I just got a new nose for the camaro, this is next on the list.
This is one tasty cowl induction hood.
F-Body Motorsports have them.

 

Good lookin Camaro you got Malc:thumbup:







Mike

 

Er, that´s not my Camaro in the attachment. I lifted that off
www.fbodymotorsports.com

 

I just wanted to point out that most cowl hoods that get put on newer cars today are completely 100% unfunctional!! The most benefit you would get would be a lower under hood temp. The origonal cowl hood had a scoop at the rear that opened like a typical forward facing scoop.

 

" a scoop at the rear that opened like a typical forward facing scoop" that it did not do, the cowl scoop is open to the rear,
at the windshield base. From the windshield base the air gets drawn into the engine compartment.
Not much more can be said.

 

I just got a new nose for the camaro,

I have a 1 piece fiberglass front end coming for my 70 Camaro. (Due Date was actually nov. 11, but that's another story). It will have a 3 1/2" cowl hood scoop. That will be almost enough height to cover the blower and the injection hat will stick through the scoop. It's not meant to function as a cowl scoop at all. Just a different look. Saw a 69 camaro set up that way. Maybe the angle of that wide flat front on the scoop will provide some down force on the front end at the traps? And should also scoop some clean air into the injection hat, Not that a blower should need any help.


I might be dreamin', but maybe the local cops won't hassle me as much if the blower appears to not stick through the hood so far (3 1/2" less than no scoop?).

 

cowl hood

well, a cowl hood releases heat out of the back which is a really good thing to have, and if you have an older car with a carb. and like me, i have an edelbrock alluminum intake which sits really high, and my flat hood wont shut over it, so cowl hoods also rise above your stuff if it sits too high, that , and yes, they do look cool.

 

snod83: I dunno if you've ever ridden in an cowl hood chevelle before, but the door opens towards the back, not the front. I got to see it dozens of times, darn kid drivers.