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post #1 of 125 (permalink) Old Mar 11th, 19, 5:52 PM Thread Starter
Mike
 
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Cowl induction benefits

Hello to everyone. Iíve searched the forum but havenít been able to get a good explanation. My newly acquired 70 SS 396 has cowl induction. Hood door is open until I start the engine, then closes. It stays closed until such time as the engine vac is almost nonexistent. If my foot is in the throttle sufficiently to actuate the switch next to the gas pedal, the electric pull-down solenoid will open the internal flapper in the hood, and assuming the external door is now open, cool fresh air will go to the carb.

Assuming this adds power to the engine, why do we limit this event to be a WOT function ? My thinking is this feature should be functioning ALL the time (assuming it actually helps).

Remember Iím a newbie to Chevelles. What am I missing ?
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post #2 of 125 (permalink) Old Mar 11th, 19, 6:06 PM
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Dan
 
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Re: Cowl induction benefits

Cool air is your friend. At cruise it is a minute benefit. At wide open throttle you may gain a small amount of power but it is more of sales gimmick in it's original form. I have a full time Cowl Induction setup on my Chevelle which does not allow any underhood air to enter the cab. It's perhaps a bit more effective than the original. That is through a 16"x 4" filter.
But Cowl Induction looks great, especially when the flapper operates as designed.
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post #3 of 125 (permalink) Old Mar 11th, 19, 7:00 PM Thread Starter
Mike
 
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Re: Cowl induction benefits

Thatís what I thought. GMís smoke & mirrors ! Thanks for confirming.
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post #4 of 125 (permalink) Old Mar 11th, 19, 8:16 PM
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Re: Cowl induction benefits

Quote:
Originally Posted by Melb-Mike View Post
Hello to everyone. Iíve searched the forum but havenít been able to get a good explanation. My newly acquired 70 SS 396 has cowl induction. Hood door is open until I start the engine, then closes. It stays closed until such time as the engine vac is almost nonexistent. If my foot is in the throttle sufficiently to actuate the switch next to the gas pedal, the electric pull-down solenoid will open the internal flapper in the hood, and assuming the external door is now open, cool fresh air will go to the carb.

Assuming this adds power to the engine, why do we limit this event to be a WOT function ? My thinking is this feature should be functioning ALL the time (assuming it actually helps).

Remember Iím a newbie to Chevelles. What am I missing ?

Not only are you a newbie, but it is abundantly obvious that you are quite young and have minimal knowledge of the design and development of performance during the "Muscle Car" era----------------of which the 1970 models were the pinnacle of the muscle car development.


TODAY, ALLLLLLLLLLLLLLLL automobiles, have an air intake system which ducts cooler, outside air into the fuel intake system. When the engine is cold, during startup and warmup of the engine, this cooler, outside air is closed off and warmer air is taken into the fuel intake system. Once the engine warms up, then the warm air is replaced by cooler outside air. It is------------AND ALWAYS HAS BEEN---------known that cooler, outside air coming into the fuel intake system will produce additional power, as opposed to hot, under hood air. The reason is because the volume of oxygen in cool air is denser than it is in warm (or hot) under hood air.


Back in the earlier days (50s-60s) of automotive performance development, ducting cooler, outside air into the air cleaner/carburetor was "high performance/hotrod" stuff. MOST of the auto manufactures offered some kind of system that ducted cooler outside air to the engine on their ultimate performance options. Only the SERIOUS hi-perf engine options had some kind of fresh air intake for the air cleaner/carb (ie hood scoop, cowl induction, scoops under the front bumper, etc, etc)
Thus, a 70-72 Chevelle with the Cowl Induction hood made a very bold statement "Hey, I'm bad".
The question is, Did the CI hood provide any added performance? Since the CI hood option on Chevelles was introduced with the 70 model, that has been debated back and forth for many years. Back in the day, one of the automotive publications (HOTROD, Super Chevy, etc) did a comparison between Chevelles with equal engine options, one without the CI hood, onw with the CI hood. The final conclusion was MAYBE, MAYBE, MAYBE, under wide open throttle at higher engine rpm, there MAY HAVE BEEN a 10hp increase in engine performance.
As I mentioned, fresh air ducted to the engine intake system was once hi-perf stuff. Today, it's common on ALLLLLLLLLLL cars.



Soooooooooo, are you missing something? Not really. You're just too young to be familiar with what it was like back in the good ole days of true muscle cars.
NO QUESTION, today's cars with performance engines will blow the doors off of yesteryears muscle cars. But NOTHING, NOTHING has the magic of an old time SS454 Chevelle, HEMI Charger, GTO Judge, W30 442, 427 Thunderbolt-------------and several others.


And with that said, the muscle cars of the 60s would also blow the doors off of the flattys-------------but I'd sure love to have a 32-34 roadster or coupe with a 300cube Mercury flatty with finned alum heads and 3 carbs, a LeSalle and a Columbia Butt.


By the way, is there anyone here who knows when/what the very first Chevy was available with ducting that provided cooler, outside air to the fuel intake system?
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post #5 of 125 (permalink) Old Mar 11th, 19, 8:23 PM
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Re: Cowl induction benefits

Quote:
Originally Posted by Melb-Mike View Post
Thatís what I thought. GMís smoke & mirrors ! Thanks for confirming.



Smoke and mirrors?????????????
NO!!!!!!!!!!!
At the time it was a TRUE performance option! Did it really work? MARGINALLY.


In my book, there is only one thing better than a 70 Chevelle with a fully functional CI hood-------------------THAT'S TWO OF 'UM!!!!!

Tom Parsons
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post #6 of 125 (permalink) Old Mar 11th, 19, 8:28 PM
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Re: Cowl induction benefits

Quote:
Originally Posted by DZAUTO View Post

Soooooooooo, are you missing something? Not really. You're just too young to be familiar with what it was like back in the good ole days of true muscle cars.
NO QUESTION, today's cars with performance engines will blow the doors off of yesteryears muscle cars. But NOTHING, NOTHING has the magic of an old time SS454 Chevelle, HEMI Charger, GTO Judge, W30 442, 427 Thunderbolt-------------and several others.
That's the way I see it.
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post #7 of 125 (permalink) Old Mar 11th, 19, 8:56 PM
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Quote:
Originally Posted by DZAUTO View Post
In my book, there is only one thing better than a 70 Chevelle with a fully functional CI hood-------------------THAT'S TWO OF 'UM!!!!!
Amen Tom!
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post #8 of 125 (permalink) Old Mar 12th, 19, 5:06 AM
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Geoff
 
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Re: Cowl induction benefits

Cold air is well worth having. Free HP. 1% increase in HP for every 10* F drop in air inlet temp. Plus, the cooler charge helps ward off detonation.
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post #9 of 125 (permalink) Old Mar 12th, 19, 11:31 AM
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Re: Cowl induction benefits

Quote:
Originally Posted by Gtogeoff View Post
Free HP.
Well, not exactly free, if you look at what they charge for the parts to restore a fully functional CI hood these days.

And if you don't already have the hood the price of that HP gets even worse!

There's a few ways to increase HP marginally for less $$, but the CI hood is the coolest looking.
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post #10 of 125 (permalink) Old Mar 12th, 19, 11:46 AM
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Re: Cowl induction benefits

If you care more for the cool look than the cool air, put a restrictor in the vacuum line going to the pot. It allows the flap to be a little more active at mid rpm's even though the inner door is still closed, and you don't have to mash your foot to the floor to show your buddies how it works. I took a plastic straight through hose connector, filled it with JB Weld then drilled small hole.
I'm going to try a yet smaller hole to see if I can get the flap to be even more responsive to the gas pedal.
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post #11 of 125 (permalink) Old Mar 12th, 19, 12:20 PM
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Re: Cowl induction benefits

Blocking off the top of the cowl helps the CI work a little bit better at the drag strip.
All I can say is,I love bashing the gas peal to the floor on the last yellow and watching that door pop open when making an 11 second pass
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post #12 of 125 (permalink) Old Mar 12th, 19, 4:53 PM
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Re: Cowl induction benefits

[QUOTE=gman628;11045042]Well, not exactly free, if you look at what they charge for the parts to restore a fully functional CI hood these days.

And if you don't already have the hood the price of that HP gets even worse!

There's a few ways to increase HP marginally for less $$, but the CI hood is the coolest looking.[/QUOTE]


There is a lot of truth in your comments-----------------but I'm especially pleased that you finally made the last comment. I was about to get unhappy with your comments, but you finally redeemed yourself.
I'm one of those people who has obsessed over CI hoods since Dec 1969.
So, when I built the 70 conv, a CI hood was a MANDATORY addition--------------------installed (with EVERY associated part) and painted, it cost me about $1400. I'd spend it again without hesitation!
As I've said before, the ONLY thing better than a Chevelle with a CI hood is two of them!


Our Malibu with a CI hood (and other stuff to go with it).

Tom Parsons
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post #13 of 125 (permalink) Old Mar 12th, 19, 5:32 PM
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Re: Cowl induction benefits

Quote:
Originally Posted by DZAUTO View Post
[QUOTE


There is a lot of truth in your comments-----------------but I'm especially pleased that you finally made the last comment. I was about to get unhappy with your comments, but you finally redeemed yourself.
I'm one of those people who has obsessed over CI hoods since Dec 1969.
So, when I built the 70 conv, a CI hood was a MANDATORY addition--------------------installed (with EVERY associated part) and painted, it cost me about $1400. I'd spend it again without hesitation!
As I've said before, the ONLY thing better than a Chevelle with a CI hood is two of them!


Our Malibu with a CI hood (and other stuff to go with it).
Totally agree, if you look at my garage pics, you'll see a CI hood on my clone.

I was just making the point that it certainly isn't FREE HP, just like any other bolt on part, it's not free!

Gary

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post #14 of 125 (permalink) Old Mar 12th, 19, 5:50 PM
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Re: Cowl induction benefits

The latest edition of ENGINE MASTERS does some testing, and cold air helps keep fuel cold, by keeping the carb cooled. So to Mike's point, keeping it closed is sort of dumb.

It is TOO COOL when those flappers open tho. Since I do enough highway in hot summer heat, I'm going all Smokey Yunick and running dryer ductwork next time.

Our 67's have VERY useless bulges Mike. Iv;e dreamed of Hilborn stacks sticking out of them... NOPE.... the bracing is all in the way. It would be a total re-engineer.

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post #15 of 125 (permalink) Old Mar 12th, 19, 9:57 PM
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Re: Cowl induction benefits

I went the Ram Air way by installing a System from the Inside Headlights to the Carb
so no Hot Under Hood Air gets into the Carb
this way whenever the Car is moving it is getting Cooler Air to the Carb

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