[YankeeRodder]

Just never thought too much about it, but what's the story with having two styles available from GM? Cost? Cheaper option to upgrade a Malibu? Why would GM offer an SS with two available hoods? What years did they offer the non functional domed hood?
I have the GM stock domed/cowl hood no flapper, and choose to run a 4" cowl Fiberglas. I like the look of the 4" myself. I keep the GM steel one safe and dry. I don't know the history of which cars got the dome and which got a dome and flapper. Why would there be two styles?

 

[Bandit1978]

Good question..I like to know too

 

[Bunz-T]

Probably because neither was referenced as cowl induction. The operating system was.

ZL2........Special ducted hood air system.

 

[jpete]

Speed costs money, how fast do you want to go?

I'd imagine the non functional hood was cheaper than the functional.

 

[DZAUTO]

The domed hoods were ONLY on 70-72 Chevelles.
Just the PLAIN, DOMED hood was part of the STANDARD SS package, PLUS it was also on the Heavy Chevy option. It was a NON-functional hood, just to add to the SS appearance.
The Cowl Induction hood was an option, as mentioned, RPO ZL2. And was ONLY available on a big block car.
In 1970, ALLLLLLLLLLLLLLLLLLLL SS cars came with a big block only (396 or 454), PERIOD.
In 71-2, an SS was available with a small block (350)------------------------COWL INDUCTION HOODS WERE NOT AVAILABLE ON A SB CAR!
ALLLLLLLLLLLLLLLLLLL Cowl Induction hoods also came with hood pins. The CI hood is MUCH MORE than just a domed hood with a flapper valve. The complete pkg requires many additional parts such as a special air cleaner with a rubber seal to mate to the hood duct, a wiring harness, relay, switch on the gas pedal, etc.

The Cowl Induction hood was more or less an additional performance feature and SUPPOSEDLY, under wide open, full throttle conditons, it MAY have added 10hp (there is no factual documentation to support this).
Sooooooooooo, bottom line, a Cowl Induction hood was basically eye candy. For me, personally, I LOVE the CI hood and have added the complete system to my 70 Malibu conv.

This is our 70 Malibu conv with the CI hood added, and it is 100% fully functional.

https://www.youtube.com/watch?v=Xra1mG1yE8Y

 

[novaderrik]

You had to pay extra to see that goofy door open and close..

 

[Alwhite00]

No idea but i loved the flapper hood on my 70. Has to be one of the coolest hoods EVER.

 

[Chris R]

Im thinking its because they could turn one hood design into two options. The standard style hood and the optional hood with a functional cowl, and to allow those that didnt want to pay extra for the cowl induction on thier SS car but still wanted the SS and thus got the standard domed hood.

 

[YankeeRodder]

Good info, I always wondered if it was $ reasons, now I know, thanks!

 

[dashboard]

Here’s my understanding of it.
When other manufactures were adding hood scoops and or some type of ram air systems a Chevrolet engineer, I forgot his name, developed the concept of cowl induction. His theory was to use the high pressure air that builds up in front of the windshield or cowl area and allow it to route cooler air into the engine compartment. The cowl induction on the 70-72 Chevelle’s with the flapper door, and that door really is cool, took things a step further and routed the cooler air directly into the air cleaner.
The idea and use dates back to some early Chevelle and Impala designs where the air cleaner was ducted directly to the cowl area.

 

[70RAIII]

all the other GM lines offered a fresh air induction system...this was Chevys offering.

 

[DZAUTO]

Here’s my understanding of it.
When other manufactures were adding hood scoops and or some type of ram air systems a Chevrolet engineer, I forgot his name, developed the concept of cowl induction. His theory was to use the high pressure air that builds up in front of the windshield or cowl area and allow it to route cooler air into the engine compartment. The cowl induction on the 70-72 Chevelle’s with the flapper door, and that door really is cool, took things a step further and routed the cooler air directly into the air cleaner.
The idea and use dates back to some early Chevelle and Impala designs where the air cleaner was ducted directly to the cowl area.

Oh, it goes WAAAAAAAAAAY further back than that. The big ole Pratt & Whitney engines on our A26 have almost exactly the same air intake system (functionally at least) as the Cowl Induction hood for 70-72 Chevelles-------------------INCLUDING a flapper valve!!!!!!

all the other GM lines offered a fresh air induction system...this was Chevys offering.

And that is exactly correct. Buick had a hood with a dual intake that fed directly into a dual snorkle air cleaner, Pont and Olds had FUNCTIONAL Ram Air hoods. Personally, I love the dual scoops on the Olds W30 hoods. Anyone remember the dual air intakes mounted UNDER the bumper of the mid-60s 442s?

 

[Les Saville]

I always wanted a CI hood, still do....

 

[71350SS]

The idea (at Chevrolet ) of the carb getting cooler air from the low pressure area at the base of the windshield goes back to the road race Corvettes of the late 50's.I think they were called the air box cars.
Also the 67-69 Z/28 had a Cowl Induction hood option.Same principle different method of delivery.
I can't remember the name of it but there's also a dealer installed air cleaner assembly that gets sealed to the cowl under the hood that was basically a road race piece....
http://www.bing.com/images/search?q...E4DB86B994E57493F0B2C767F2C5&selectedIndex=33
IIRC there was some kind of controversy if this was ever offered on 66 or 67 Chevelles.
So the CI hood of the 70-72 Super Sports had more to it than just a money making idea but if Chevy (back then) could provide extra performance and make money doing it,then more power to them. JMO

 

[Gmsport]

Interesting thread. If I remember correctly, I read a while ago that chevelles cowl induction was the best hood design (offered by GM) in introduce cooler air into the air cleaner. The base of the windshield was found to be the best place for it. The ram air on the 442's was also a good option but lost volume as speed increased due to the front of the car deflecting air upwards. The Buick GS and the GTO was least likely to "grab" cooler air at speed due to air deflecting off the front of the car and not skimming along the top of the hood. They actually mentioned, that at high speed, there was diminished air at the center of the hood (GS/GTO) with most air hitting the windshield.

I personally always like the the chevelles CI hood. And my second choice would be the 442 hood.

 

[ToocoolZ28]

You had to pay extra to see that goofy door open and close..

Obviously you don't have one :noway:.

 

[70RAIII]

I heard the only "fresh air" setups that worked...were the under the bumper Olds set ups and the '70-'75 Firebird Formula hood set ups(when functional). I like to watch the flapper on my T/A open and close.... I really don't think ti does anything though...

 

[novaderrik]

Obviously you don't have one :noway:.

never would, either... they did it right on the 69 Camaros- just grab the cool air at the base of the windshield with no external moving parts to get damaged or distract you while you are driving... they had flappers, too, but they were at the back of the hood out of sight to the general public and served to keep gas fumes from getting into the heater thru the cowl when the engine wasn't running. function following form with no unnecessary bling.

 

[DZAUTO]

The only thing cooler than a Chevelle with a functional Cowl Induction hood---------------------is two of them! Even if it does cost more.
By the time I ordered the new CI hood and ALLLLLLLLLLLL the related parts and had it painted to match, I had about $1400 invested in it---------------and that was back in 98. I have ZERO regrets today!

 

[70SSTHUMPER]

never would, either... they did it right on the 69 Camaros- just grab the cool air at the base of the windshield with no external moving parts to get damaged or distract you while you are driving... they had flappers, too, but they were at the back of the hood out of sight to the general public and served to keep gas fumes from getting into the heater thru the cowl when the engine wasn't running. function following form with no unnecessary bling.

With this response in mind, it generates the question:

1.) If the SS hood was not actually "Functional" as stated in earlier posts in this thread, how did the 69 Camaro with the same mechanical style (domed) only with a flapper behind the cowl or edge of the hood?
Wouldn't the SS hood provide some functional fresh air (cooler) then a stock Malibu hood?

2.) As I understood it, air flowed over the surface of the hood and created a "low" pressure zone at the base of the windshield, when the CI flapper opened it "pulled air into the sealed air cleaner? In other words the CI hood acted much like a wing, creating a low pressure on top. Many people do not know that when a plane is propelled forward (thrust), it's the shape of the wing that actually creates a low pressure area on top of it. Planes stay aloft with thrust because the wing is picked up from that low pressure. Not a higher pressure under the wing as many people think. Weird huh? Does CI mimic the principal of the wing?

Am I totally out to lunch here?