Well, thought I'd share my recent hood modifications. Decided my formula need a cold air intake, preferably one that might even make a slight postive pressure!

Anyway, I attached a sheet of aluminum to the inside of my hood. Then cut a hole for the air cleaner assembly to seal to, and made a grille for the cowl opening to let the air in.

Here's a pic of the grille I made. I'm really pleased with the way this turned out.

http://groups.msn.com/Mytrucksothers...to&PhotoID=222

This one is with the aluminum sheet attached but not polished yet.

http://groups.msn.com/Mytrucksothers...to&PhotoID=226


This next is the air cleaner assembly I built.. I started with a 73 chevy truck base, then cut the snorkel off and welded the holes shut. Then I drilled some drain holes in the bottom, though i've never seen water in here yet, and attached the hood weatherstripping from an 84 buick. This angle shows where I welded the snorkel shut.. you see it? Also notice my Jamex bar fits right in front of the filter assembly.


http://groups.msn.com/Mytrucksothers...to&PhotoID=259

This next pic is after I polished the hood sheet. It couldve been much better if i'd sanded the hood first, and theres a few blemishes and scratches in it still. All I did was use Flash metal polish. First the precut then their billet polish.

http://groups.msn.com/Mytrucksothers...to&PhotoID=263


I ran this set up for awhile with just an open element. I could definately feel the difference between that and the open element and no hood. After building the sealed base I really havent noticed any difference.. but I do like the blue filter!!

 

Whats with TGO and MSN anyway? I can post pics on other sites just not here?


Still can't get it to show the pictures.. or even go directly to the pic link.. But this will work I guess. If anybody knows how to show msn pics please let me know.

One more try..

 

WOW! thats some awesome work man..two thumbs up!!:hail:

 

Good job. Think a K&N Xstream airfilter top would help any?

 

Wow we were just talking about doing this in the Ram Air thread.

Looks awesome, I think I will try that.

-But, I thought those hoods were already functional, arent they. I mean my car has a bunch of stuff on it that makes it look like it works.

 

Early cars were functional.. But they had some big clunky lookin contraption that let air in through a small hole in the top of the filter element. By 87 these hoods were just blocked off. I didnt like the looks of the stock setup so I went this way. You should hear the vacuum noise it makes now! Sittin idling you can hear the carb suckin through the hood vent, and if you crack the window you can hear it whenever you accelerate while driving.

 

Some cars had a functional air scoop from the factory that was similar to your setup.

I would consider an X-treme air lid to further improve air flow.

I will be the first to say don't drive in the rain!

Yea the img function doesn't seem to work from MSN.

 

woah, thats really wild, I like that.

 

As for driving in the rain, we get 140" a year here.. The setups been on bout 2 months and i've never seen water get into it yet. Initially I was worried bout it. .but looks like its allright. And yes i thought bout an xtreme lid.. but spending my money in other areas so it'll have to wait.

 

It was the early Trans Ams that had the functional power bulge hood...I wanna say up until 84...then the T/As had the flat hood with the vents near the front...when the Formulas came out in 87 they had the power bulge hood as well, but only for cosmetic reasons. Also not all early T/As that had it had a funcitoning one either. For example my 1982 was the LG4 4bbl carb setup and it had the non functional hood although the scoop was cut out and open. The 82 LU5 cross fire injection Trans Ams had the cowl hood induction system on them. Although I've heard they have a tendancy to break. Then again they're 20yr old cars. =)

 

What did you use to make the cowl grille? I want to open mine up to get rid of some hot air in the engine compartment but dont want any leaves in there.

 

The earlier cars had scoops that had two pieces blocking the opening. One piece was a flat plastic piece, the other was lots of honeycombs, which you could use to prevent leaves. Honestly, leaves is not a thing to worry about.

This is only for a car thats not a daily driver. We can't forget about rain.

 

Well my car is a daily driver.. in a very rainy area. We're at the southern tip of the only rain forest in the continental US. We've had years with over 140" of rain. I've had my hood open for 2 months now. Never found more than a drop of water that made it all the way to the air cleaner. Never had water get in there while washing the car, and i've hosed that area down. The aluminum sheet is formed to the inside of the hood. Water doesnt flow towards the air cleaner but along the sheet to the sides. I do not have a garage or car port. This thing sits outside all the time.. No problems!!

 

great looking job.

 

if you do do that without having it lead directley to the air cleaner like he did, your car might start cutting out if you get water on your distributor cap.

 

Someone correct me if I'm wrong... but I thought cowl hoods were meant to pull air from underneath the front clip, through the engine bay, and out through the cowl opening. Doesn't the aluminum sheet prevent that? The only reason you would enclose the air cleaner like that would be for a ram-air setup. I just don't see the point here.

 

Heh... I guess I stumped everyone on that one, huh? The more I think about it... the faster you go the more your engine will choke, because it won't be getting enough air in the mixture. Cowl hoods work with the vaccuum created on the windshield at high speed. Air goes straight to the windshield, then up and over it. This would cause air in the engine bay to be pulled out through the cowl opening due to the vaccuum being created on the windshield. With the air cleaner sealed off like that, it's pulling air out of the intake (well not really, but it makes it a lot more difficult for air to go in)! You might want to rethink this.

 

How did the original cowl induction system on the early CFI cars work then?

 

OK, I'll correct you. The cowl hood draws air from a high pressure zone at the base of the windshield. Even though you could be travelling at 60MPH, the air would be sucked into the aircleaner area via a pressure differential. A minor supercharging effect.

 

Yeah if I remember correctly the orignal cowl induction system on like an 82 CFI car would have a flap behind the cowl and at speed it would open up and cause a vaccuum effect that would draw air into the air cleaner.....my friend has one on his car and you'd hear it when it opened up and like Marc 85Z28 said it would cause a minor super charger effect

 

Yes there is a high pressure area at the base of the windshield. This shoves air down into the air filter. GM has used cowl induction for years, and not just with raised hoods. Some 60s muscle cars were plumbed into the firewall and sucked air from the vents at the bottom of the windshield.

I had a 72 malibu myself with a factory cowl induction hood put on it. This hood had a flapper that popped up out of the hood into the high pressure area. The flapper was spring loaded with vacuum holding it closed. So whenever vacuum dropped the flap would pop open. This also means that whenever the motor was off the flapper is open. Same sort of setup as I put on my bird. Still didnt get water in the air cleaner.

I've also heard that the cowl induction actually creates more pressure at the air filter than ram air did. Not sure if this applies to 3d gens though. The early muscle cars like chevelles had more of a straight up windshield, which might have created a larger pressure differential.

 

Man, I suck... Looks like everyone else is right. It doesn't seem to make sense, that air would hit the windshield and actually go down into the cowl instead of up and over the car, but that seems to be what's happening. Oh well, thanks for correcting me.

On a side note, as I was reading some more detailed info about this, the ram air setup created more pressure than the cowl at the air cleaner, but the ram air caused a lot of turbulence going into the carburetor, causing the cowl setup to actually create more horsepower.

 

Looks good!
Check out how PHR did this to an 87 Formula, way back in 1987...
http://www.hioutput.com/tech/air.html

Pete