Why was there a cowl hood without, and cowl hood with flapper offered? - Chevelle Tech
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post #1 of 59 (permalink) Old May 11th, 14, 7:01 PM Thread Starter
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Question Why was there a cowl hood without, and cowl hood with flapper offered?

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?
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post #2 of 59 (permalink) Old May 11th, 14, 7:38 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

Good question..I like to know too
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post #3 of 59 (permalink) Old May 11th, 14, 7:41 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

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

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post #4 of 59 (permalink) Old May 11th, 14, 8:09 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

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

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post #5 of 59 (permalink) Old May 11th, 14, 8:23 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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.



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post #6 of 59 (permalink) Old May 11th, 14, 8:50 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

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post #7 of 59 (permalink) Old May 11th, 14, 9:16 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

Tighten it till it strips and back it off a quarter turn.
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post #8 of 59 (permalink) Old May 11th, 14, 10:24 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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.

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post #9 of 59 (permalink) Old May 11th, 14, 10:55 PM Thread Starter
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

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post #10 of 59 (permalink) Old May 11th, 14, 11:47 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

Hereís 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 Chevelleís 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.
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post #11 of 59 (permalink) Old May 11th, 14, 11:59 PM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

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post #12 of 59 (permalink) Old May 12th, 14, 12:44 AM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

Quote:
Originally Posted by dashboard View Post
Hereís 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 Chevelleís 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!!!!!!

Quote:
Originally Posted by 70RAIII View Post
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?









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post #13 of 59 (permalink) Old May 12th, 14, 12:54 AM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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

Les Saville



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post #14 of 59 (permalink) Old May 12th, 14, 2:07 AM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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=...lectedIndex=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

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post #15 of 59 (permalink) Old May 12th, 14, 11:17 AM
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Re: Why was there a cowl hood without, and cowl hood with flapper offe

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.
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