This winter I am probably going to add the Cowl Induction flapper. I got to wondering if that would do anything for HP. I figure that it is just a show-peice and really didn't do much as to the induction of cold air. I am putting on anyway because I think it is very cool, but just figured I would ask about the HP loss/gian. Thanks in advance,
Chris

You'd probably gain a 10th in the quarter by running no hood at all, I can't believe how heavy my cowl induction hood is, it's gotta weigh 120lbs!

Thanks bob. I really don't do much racing at the track due to they just shut ours down, and its more of a show/driver. So you didn't notice an loss/gain of power due to the hood, just the added weight?
Thanks,
Chris

cold air from the cowl area is very adventagious,escpecially if your air cleaner seals as it is supposed to. As far as feeling the difference that depends on how well your feel is for the car, but the cold air charge and its velocity will definately help. thats why the stockcars suck air from the cowls. Ralph

I think after a full cool down period at the track it would run better without the cowl induction. After the engine compartment is warmed up I would say the Cowl Induction system works the way it should in bringing cooler air to the carb.

I agree about the weight of the hood and the gain in E.T. Plus you have the ultimate cool air advantage.

One of the magazines tested the theory, and they stated it does nothing to improve time in the 1/4 mile. Maybe it adds enough HP to offset the weight, who knows - but it looks cool and is one of the signature parts of a '70. graemlins/thumbsup.gif

I will not express ANY opinions regarding any HP increase resulting from a properly functioning CI hood.
But, here are some facts. A properly installed and sealed (resulting from the seal between the hood duct and the air cleaner) CI hood WILL deliver cooler air from the base of the windshield. Regardless of whether the OUTER flapper is functional or not, the air still has a clear path to the air cleaner. Below, and behind, the rear lip of the CI hood is where the REAL opening to the hood duct is located. So, even if the outer flapper remained closed during full throttle or power conditions, the cooler air can still get to the air cleaner. The INNER door is what admits the cooler air to the duct, and that door is actuated electrically by a switch located at the accelerator pedal (engaged at full throttle). Now, if the INNER door is completely removed, as well as the frame for the inner door, this will allow a FULL TIME, unrestricted flow of cooler, denser outside air to the air cleaner. Thus, it would appear that the PRIMARY function of the OUTER door is mainly for show. In my opinion, (Ooops, I wasn't going to offer an opinion) a properly functioning CI hood and outer door is the neatest/coolest hood ever available in the history of factory, performance automobile options. Period.
Back to the facts. As we all know, the more air that can be introduced into an internal combustion engine, results in more output. Along with that, is also more COOLER air, which is denser than hot air. Once the compartment under the hood of a car is fully heated up by the engine, the air is CONSIDERABLY hotter than the air at the base of the windshield. Plus, the air at the base of the windshield of a moving car is somewhat compressed (denser). Cooler, compressed. If you have ever seen the hood open on a NASCAR race car, you may have noticed that the air cleaner is fully enclosed with a duct that goes to an opening at the base of the windshield. ONLY cooler, outside air is fed to those engines, no under hood hot air. Why? This is 2004, the CI hood was introduced in 1970 (before some here at TC were born)---------------- AND NASCAR STILL USES A NEARLY IDENTICAL DESIGN!
So, can cooler, ducted, outside air from the base of the windshield provide an added charge that would result in a HP increase? Theoretically, yes. Seat of the pants? Not likely. On a dyno? Probably, but minimal. Is a 70-72 FUNCTIONAL CI hood trick, cool, impressive, neat and desireable? Yep, it's the ultimate factory hood, ever!

Thanks guys. Tom, you answered my question and then some. Great explination. As far as your opinion, I couldn't agree with you more. It definately is the coolest. Thats why I want one. The origonal owner of the car didn't have one orderd, but 100% correctness is not on the docket for my car. I wasn't installing it for any gains. But another question along with my limited understanding of aerodynamics is wouldn't the flapper door opening under acceleration create a "bump" in the limited aerodynamics of these cars causing that cool dense air to bypass the door and go to the windsheild. I really don't mind it, but I just like to know if these things really worked.

Tell me if I am correct here. In summary the door itself does not do that much in the cool air induction but it is the Cowl Induction Hood (the part near the back of the hood/base of windsheild) and not the door that does the greatest amount of cool air induction?

Thanks for the great replys and info,
Chris

P.S. Now I can't wait for my car to go to body this winter and get the door put on graemlins/hurray.gif and get the body straightened and re-sprayed.

I thought everybody knew it's worth at least 150HP when bench racin!!!
:D graemlins/waving.gif :D

Originally posted by Big James 4XL:
I thought everybody knew it's worth at least 150HP when bench racin!!!
:D graemlins/waving.gif :D Thought it was worth that much, thanks for THE definitive answer.
Chris tongue.gif

Chris,
I'm not sure, but I almost think that I understood from your reply that you plan to add the outer door for your hood. Right? You can't add the flapper door to a non-CI hood---------------you have to add the whole CI hood. Even though the domed hood was on all 70-72 SS Chevelles, and it is the same shape as the CI hood, it is a totally different hood. The domed DOES NOT have the the inner ducting. Plus, the domed hood is simply that, a domed hood. The CI hood is a system pkg which includes LOTS of additional parts, inner/outer door parts, wiring harness, vacuum parts, relay, gas pedal switch, air cleaner parts, etc. Even if you fabricated some way to install the outer door on the SS domed hood, you still would not have the necessary ducting to direct cooler into the air cleaner.
As far as the outer door affecting the airflow into the under side of the hood where it goes into the ducting, nah, I doubt that it does.
As I mentioned before, you could completely eliminate the INNER door, frame and actuation components so that you would have full time outside air flow into the air cleaner, and only have the outer fully functional for looks. Even though the CI hood on my 70 is 100% fully functional as it was from the factory, I have seriously considered removing the inner door and frame.
Both the 69 Z-28 and mid 70s Vettes had true CI hoods, BUT, neither had that trick outer door which opened under hard acceleration, nor did they have those neat chrome COWL INDUCTION emblems on the hood. The CI hood completely changes the whole personality of a 70-72 Chevelle. Even an SS with just the domed hood doesn't have the same image as an SS with the CI hood.

I raced my 70SS for years. It had the domed hood, not the cowl hood with the trap door.
I made the cowl hood functional by removing the spot "welded in" plate in the rear, and adding an alum panel that enclosed the underside of the hood so that it had to breathe through the rear opening of the cowl. Then I made up an old aircleaner base to mate with my alum panel. The air cleaner base didn't have an element in it, just a piece of foam rubber that glued where the element would have been. It mated with the underside of the hood when closed.
This was worth 2 tenths and 2 mph on my car.
When the air was good, the old girl would run high 11's, so I had to put the air cleaner back on to keep it in the 12's, and keep the tech guy from booting me.

Tom, yea I know you need the whole new hood and I am getting the new Goodmark one with the cutout and then putting on the door and the other parts. So the door will not effect the airflow into the motor that much and would not cause the power to decline (If i am reading it all correctly)? Sounds good then.

I do have the domed hood on my SS now, but a previous owner did as Ron454 said.

Thanks a lot guys for all the help.
Chris