Has anyone ever made a sheetmetal box that goes either on to of or below the carb and seals against the cowl hood?? I have a 4" cowl and want to make some sort of something to seal the carb and filter inside and breath fresh cold air through the cowl hood. Now wouldn't it be better if the carb was inside too that way it is away from underhood temps? Anyone ever done this??

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Confucius says " he who uses small, crimped exhaust, gets short of breath"

Yeah, do a search under cowl induction or something. I had a topic going about it a while back.

Your talking S.O.P. for most any bracket racer Bruce. You can make the pan out of aluminum, plexiglass, most any semi-rigid material. Cut a hole the same size as the top of the carb (for Holleys you will also have to drill holes for the float adjustment screws). You can get 2" x 4" foam at Home Depot or other hardware stores and just trim it with an electric knife to seal snug against the underside of the hood and firewall. Make sure you have a couple of inches clearance above the vent tubes for airflow.

<font face="Arial,Verdana" size="2">Originally posted by Marv Davis:
Cut a hole the same size as the top of the carb (for Holleys you will also have to drill holes for the float adjustment screws). </font>


Ya think it would make a differance if I made one so the whole carb is inside and sealed away from the engine heat?

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Confucius says " he who uses small, crimped exhaust, gets short of breath"

So you would cut the base plate the same as the intake flange? then install the base on the intake, then the carb? That would work as long as you use a carb spacer to keep the linkages from binding I guess. All of the linkages, fuel lines, etc hangs below the carb base plate and would need to come through your base plate. Sort of defeats the purpose IMO.

I can tell you I was deeply dissapointed by the results. The following link gives you the rundown.

http://www.nastyz28.com/ubb/Forum8/HTML/009080.html

I've thought about trying it again only this time have NAACA ducts cut into the cowl so the intake would be forward facing w/o having a big honkin' scoop to look around.

[This message has been edited by HEAVYchev (edited December 21, 2004).]

I'm forced to ask how much surface area can a 3" cowl provide at its opening? Is it even the same surface area as your air filter? I think a 3" cowl is just too small to be functional. Not sure though, anyone know for sure?

I went on avg. out of 4 runs .2 sec quicker with my homemade cold air/ram air set up

I cut a 14" round hole in the hood, rivited on a 427 stinger vette style scoop

Bought a big rope handle red plastic bucket at the dollar store for $5 (16" at the bottom and alot bigger at the top)

measured the height from bottom of air cleaner to bottom of hood.

cut bucket to that size.

Cut a hole in the bottom center on bucket alittle bigger than the hole in the bottom of my air cleaner.

drilled 4 holes through bottom of air cleaner and bucket.

Put silicon around the hole in bucket, placed air cleaner bottom in bucket over hole and shot 4 rivits in the 4 holes I drilled

Put foam PVC pipe wrap stuff around top edege of bucket (got it for a buck at home depot)

Then put the bucket/bottom part of air cleaner on car, put filter and top on like norm. The foam seals to the bottom of the hood when it's closed

I run a 10" dia edelbrock chrome cleaner with a almost 4" tall K&N filter.

The top sticks up through the hood about 2.75" and my rivited on scoop is open in front and rear. 3" in front. 1.5" in rear

i made a aluminum air pan for my L88 hood. it's the exact dia. of the scoop area or 30"x21"x3".i made it out of one piece of sheet metal and made the sides using a metal shear/brake in our race shop.i even rolled the edges for more support and rigidity.
this is how i measured it to fit i took a measurement from 1" out from the firewall cowl area to the center of the carb. i then cut out a circle of about 6"dia. then i riveted onto the sheet metal a flat base 9" dia. air cleaner.the wall or sides of the air pan are 3" high to within 4" of the fire wall were it droppd down to 1.5" high.now to seal it against the hood i used 7/8ths i.d soft foam pipe insulation.
i noticed a little more performance by doing this and the engines seems to run a little cooler to

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1972 chevy camaro ss 350 sbc 425 hp/356 @ the wheels,350 trans,373 gears,daily driver with restification in progress for that old school day 2 look ------- future plans- turning it into a baldwin motion Z30 clone
"IF IT'S TO LOUD YOUR TO OLD"
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<font face="Arial,Verdana" size="2">Originally posted by marsfrogie:
I'm forced to ask how much surface area can a 3" cowl provide at its opening? Is it even the same surface area as your air filter? I think a 3" cowl is just too small to be functional. Not sure though, anyone know for sure?</font>

If four 2" butterflies in a 1200cfm Dominator = 12.56 sq. inches of surface area, a 2" x 10" cowl opening ought to allow ample airflow for anything under 600HP. More important is dirrecting airflow and restricting flow into the carb. Word I hear is the bottom of the cowl needs to be 2" or more above the top of the chokehorn / bowl vent tubes.

Here's one clean, simple design for an airpan (http://www.small-block-chevy.com/coldair.jpg) Bruce.

The examples given are all forward facing scoop designs, including the link Marv posted. Without a doubt, any forward faced design has it's merits, especially at high speeds on the top end since you ARE ramming the air into the carb. It's whether to believe the hype about high pressure areas at the windshield that comes into question and whether this can be utilized. Maybe you can be more successful than myself, but keep these things in mind.

1. You trap heat below the airbox, which radiates into the fuel bowls. ( notice dragsters using scoops use an air bell or velocity stack which raises the box above the carb and allows the heat to escape and air to circulate)

2. You are asking the air which is present at the windshield to turn 180* and back-flow nearly 2' into the carb, once it overcomes the turbulence.

the neatest way to make your hood function is to take the hood off and flip it over and use a very thin but stable sheet of alum. or other metal and make the hood flat on that side.(cover the cowl up)...fiberglass it in.... find the area for your carb and cut the hole for just your air filter to stick into the cowl hood......use othe means to control heat issues like block off the heat cross over ,insulate the fuel lines , install a splash shield under the intake, run synthic oils , cooler thermostate, so on and so on........

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1980 z28 3900lbs daily driver,414ci bbc,13.505 @107.19 mph w/2.15 60ft. 2.73 gears in street trim.

1981 camaro "the race car" as the kids say. 454 .060 over 13.5 to 1 comp.roller cam,tunnel ram w/2 600 carbs, 4500 stall and 4.10 gears...under recostruction on chassis and engine mods.

1986 ford pick-up "the tow rig" runs a slow 18.00 flat at 75 mph in 1st and second gear only.

[This message has been edited by ddeennis (edited December 23, 2004).]

The area at the cowl is a low pressure zone therefore a great location for outside air into the carb. All your trying to do is pull low temperature air into the carb compared to high temp underhood air.

<font face="Arial,Verdana" size="2">Originally posted by HEAVYchev:
The examples given are all forward facing scoop designs, including the link Marv posted. </font>

No that's the setup I have on the Nova with a 2" cowl hood Bill. I've ran with the air pan, and without and not found a lot of difference in performance. Probably only because I do a complete cooldown between laps if possible and bring the car to the line at the same temp every pass.
But it's more consistant and easier to dial when underhood temps arent screwing things.

i used to wonder if cowl induction hoods would force air into the engine until i tested it last summer.i taped pieces of yarn on my windshield,every piece within 3inches of the cowl was pulled towards the engine. as soon as i took off forward from backing out they went towards the engine.how big of a filter do you need to use?i have a setup like Marvs' but with a 10" filter

<font face="Arial,Verdana" size="2">Originally posted by ccrider:
i used to wonder if cowl induction hoods would force air into the engine until i tested it last summer.i taped pieces of yarn on my windshield,every piece within 3inches of the cowl was pulled towards the engine. as soon as i took off forward from backing out they went towards the engine.how big of a filter do you need to use?i have a setup like Marvs' but with a 10" filter</font>


Could you clear that up? Are you saying that the yarn blew AWAY from the engine when you went forward? Or are you saying it always goes toward the engine?



[This message has been edited by marsfrogie (edited December 23, 2004).]

as soon as the car went forward the yarn was sucked into the engine compartment.all of the yarn pieces,about 6" long,were pulled into the hood opening.it always went into the engine.

I've decided to just build a heat shield for the bottom of the carb, and build a pan for the top of the carb. Like Marv said it would be to hard to seal the whole carb in.

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Confucius says " he who uses small, crimped exhaust, gets short of breath"

A round baking dish the same diameter as the hood ring works good for an air pan. Just cut it to height and cut the carb hole. Then screw the air cleaner base to the inside of the pan to mount it. Then cut some rubber line down the middle to use for a seal. I've seen it done and it looked good, not cheesed up.I would never of known it was made from a baking dish had I not asked the guy where he got it. If you use an aluminum one you could even polish it up real nice. I was thinking about making one the same, but the flaps on my stock 80 hood don't look like they flow too much air?

I simply cut the hole in my hood with a 16" diameter. I split some fuel line to put on the edge of the metal. (less than 1" space around the air filter) The air filter sits almost completely above the hood and is almost touching the 3" cowl.
When I built the cowl for my S10, the first time it rained I noticed raindrops would run up the hood, and up the cowl towards the windshield and when they got to the edge of the cowl they would do a 180* and go right into the cowl, straight for the air cleaner!
The "High pressure area at the base of the windshield theory" Is complete fact.
As ccrider said do a yarn test.

The whole "air pan" thing is a bit of over kill imo. There is far more air going down the cowl (3") than you engine can use and will just go past the air cleaner and certainly do no harm. It would be useful while you're not moving though, serving as a heat shield.



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73RS/LT/427

ZS10... I agree and disagree with you on that.

Yes a cowl scoop/hood will bring in more than enough air, but what does hot air do? It goes up right?

With a sealed air pan, atleast my thought on it is.. to seal the hot under hood air out of the carb's intake air flow, and not let the cool outside air mix with the heated under hood air.

I don't really care about the whole 'ram air' thing, cause it's been proved that it's ture/works but only helps at speeds of 100 mph and up. Most of use don't spend much time at those speeds. Just at the top end of the track.

I care about keeping the coolest flow of air I can get to the carb. That's what makes power. 1% power gain for each 10-12* drop in intake/carb inlet temp.

I do run a 'ram air' scoop cause I like the looks of the vette stinger style, but the back is open and close to the windshield just like a cowl scoop..


Oh yeah 1 more thing, all that extra air going through a non sealed scoop, and into the engine bay.. Won't it build up? Comes in faster than it goes out, and if i'm not wrong that would = more aero drag and lift. Last thing we would won't is more front end aero lift at the top end

[This message has been edited by night rider (edited December 25, 2004).]

Just to give a bit more confirmation on the cowl induction my IAT (intake air temp)sensor in my plenum will show up to 150-160 degree temps at idle and basically ambient temps under wide open throttle. I don't run a pan just a K&N filter and top. Part throttle temps still run fairly high due to the lack of a pan or isolation. Although I don't make it a habit to run in the rain on Power Tour we simply had no choice. Driving down the HWY rain would fall down the windshield and off the back of the cowl and suck right into the opening. A very visual example of the airflow.

Does it make more power? Don't have a clue, I'd guess it doesn't hurt a bit.

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70 SS 454 CI Dynoed 684 HP, 702 TQ All Aluminium Fuel Injected Small Block , plus 200 - 500 HP NX nitrous system.

<font face="Arial,Verdana" size="2">Originally posted by night rider:
ZS10...
Oh yeah 1 more thing, all that extra air going through a non sealed scoop, and into the engine bay.. Won't it build up? Comes in faster than it goes out, and if i'm not wrong that would = more aero drag and lift. Last thing we would won't is more front end aero lift at the top end

</font>

This makes sense, but I don't think I would have to worrie about this cause I removed my inner fenders, so the air has plenty of room to escape.



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Confucius says " he who uses small, crimped exhaust, gets short of breath"

as far as trying to isolate the whole carb from the under hood temps WOULD be difficult to seal it all up. but if you are sucessful to seal the incoming air from the under hood air that would be probablly good enough.

however you could also run an ice can on the fuel side so that all that is going into the carb is cold. and as more cold fuel and air flows through it. the carb would drop temps.
besides if both the air fuel were cold it probablly wouldn't make a huge diffrence to flow through a slightly warmer carb. neither of the two are in there very long anyway.

bryan1970.. Has the right idea about keeping the fuel cool too, but didn't NHRA outlaw "cool cans" a few years back. I may be wrong, but I thought I heard something like they banned em'

I do run a fuel cooler on mine. (trans cooler) med. size tube/fine one, in front of my rad., next to my trans coolers, and have the fuel supply line plumbed into it. No test done to see if it really helped but it couldnt have hurt any

I made a few back to back runs and picked up about .1 sec in the 1/8 mile with it


http://www.supermotors.org/getfile/163586/fullsize/DSC00396.JPG
http://www.supermotors.org/getfile/162743/fullsize/DSC00392.JPG

[This message has been edited by Mwilson (edited December 26, 2004).]

i really don't know if NHRA outlaws the cooling cans for the fuel. or if they are are only outlawed in certain classes maybe?

i DO know that they work great. even with just plain ice in them they work great. but dry ice works better. but is on the expencive side after a while. remeber if you do run a can rejetting WILL be inorder.