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Hood scoop?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bad_bo_ti, Mar 23, 2000.

  1. bad_bo_ti

    bad_bo_ti 1/2 ton status

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    i was wanting to get a 4-4.5 inch rise cowl induction hood scoop, not the full hood just the scoop. i was wondering if anyone knew of a place that had them for cheap, I might go with a full cowl induction hood if anyone knows of one of those for cheap too. please list phone numbers or websites. thanks.
     
  2. BurbinOR

    BurbinOR 3/4 ton status

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    Check with Shawn Spickler, his rig (which is beautiful) has a cowl hood, think he paid $300 for it. Nice unit.........

    '79 - 406 w/IROC TPI - K5#5 - a <font color=orange>sickness[​IMG] <font color=blue>you never get enough of!! [​IMG]
     
  3. Eagle86K5

    Eagle86K5 1/2 ton status

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    J.C.Whitney has some fiberglass ones in the catalog...

    <font color=green>Eagle86K5[​IMG]

    <font color=red>Only guy I know that can get out of line in a one car funeral
     
  4. OLDSTEEL

    OLDSTEEL 1/2 ton status

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    P.A.W. or Summit have a lot of scoops to choose from. They will normally match or beat others prices.

    74 K5

    Leave it like you found it, or better!
     
  5. Shawn

    Shawn 1/2 ton status Premium Member Author

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    I purchased a cowl hood from Unlimited Fiberglass. It was the cheapest I found at that time. After getting it, I wasn't too happy with the way it fit. The gaps seemed bigger in some areas than others. When I finally got the K5 painted, the body shop had to spend many hours prepping it which ended up costing me more then if I would of just purchased a quality hood like Harwood. I have to admit it is much lighter than stock. It does have the metal braces in it and uses the factory hinges, springs and latch so there's no prop rods or hood locks like you see on others. It's also been proven that cowl hoods help keep the engine compartment cooler since air flows out towards the windshield. I'm not sure what the other brands are like (Summit, US Bodysource, etc). Hope this helps.

    I attached a body shop pic-

    Frank- Thanks for the comment!

    Shawn Spickler
    87 K5
     
  6. BurbinOR

    BurbinOR 3/4 ton status

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    You're welcome, that is a NICE truck.

    Do you notice any excessive heat in summer from the cowl hood finding its' way into the cab? My 71 SS 396 Camaro did after I put on the cowl induction hood on it.

    '79 - 406 w/IROC TPI - K5#5 - a <font color=orange>sickness[​IMG] <font color=blue>you never get enough of!! [​IMG]
     
  7. Shawn

    Shawn 1/2 ton status Premium Member Author

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    I haven't noticed any excess heat coming in when I have the vent off but when I turn on the vents it does seem the air is warmer. Usually I just roll down the windows. I'm sure when (and if) I get my AC going again, it will affect it a little.

    Shawn
    87 K5
     
  8. Blade

    Blade Registered Member

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  9. Steve88

    Steve88 1/2 ton status

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    Hey Shawn, granted you have a fine looking truck. Wish mine could look as nice someday, but I've got to ask you where you saw that the airflow would be towards the windshield with a cowl hood? Someone who really knows about this correct me if I'm wrong, but a cowl-hood will force more outside air under the scoop into the engine compartment (or as it was meant to be into your cowl-induction air-intake like on the ol' Camaro's) rather than the air flowing out from the cowl.

    Right? [​IMG]

    <font color=red>Steve88</font color=red>[​IMG]
    88K5 Silverado
    thunderdog@metallica.com
     
  10. Shawn

    Shawn 1/2 ton status Premium Member Author

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    When I was shopping for mine, I called a few cowl hood companies and checked on this. Basically at high speeds the air will bounce off the windshield and get forced in the cowl. It's nothing like ram-air or anything and I doubt you'll gain much performance from this. At lower speeds, you will have the hot air coming out which keeps the engine compartment cooler. I can actually feel the heat coming out if I put my hand behind the cowl. The radiator fan itself is pushing the air out at a stop or at low speeds. This is important to me when off-road since I want to keep the big block cool as possible.

    Shawn
    87 K5
     
  11. Steve88

    Steve88 1/2 ton status

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    Well I'll take your word for it, but I sure seem to remember those Camaro's (Chevelles too?) getting a boost from the pressure fed intake (?) I doubt you'd be feeling any heat if your intake was built around the cowl hood like those old muscle cars.

    Regardless your truck is one awesome looking piece of work !!! I'd love to do a cowl hood on mine...

    <font color=red>Steve88</font color=red>[​IMG]
    88K5 Silverado
    thunderdog@metallica.com
     
  12. Shawn

    Shawn 1/2 ton status Premium Member Author

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    Oh yeah, I remember too since I use to have a 68 Camaro. They had a functional cowl where the a duct was installed and I think there was a flap that was connected to you carb linkage. This would give you some added performance since your now forcing air to go in your carb. There was a big difference in price on the functional/non functional cowl hood for these cars. All cowl hoods made for the GM trucks are non functional. Would be cool if they made a functional though!

    Shawn
     
  13. Eagle86K5

    Eagle86K5 1/2 ton status

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    Now I am not sure....but being a pilot I would guess that....air coming over the hood would create a high pressure area like on a wing of a plane, and a low pressure underneath it. As the air hits the windshield it would cause it to suck the wind from underneath the hood out over the windshield. This increase in air would have a sort of ram effevt to the intake in the path of the air exiting the rear of the hood. This siphoning effect is called Bernoulies principle and is the same thing that causes a carb to work.

    <font color=green>Eagle86K5[​IMG]

    <font color=red>Only guy I know that can get out of line in a one car funeral
     
  14. Steve88

    Steve88 1/2 ton status

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    I'm no aviation person, but I believe that would only be true if the hood were more shaped like a wing, but since the air underneath the engine (i.e. the "bottom" of the wing) has no effect on the air on the top of the hood I don't know if you can really compare it to a wing. I think Shawn summed it up with the comment about the functional cowls vs. non-functional cowls.

    Aw, what the heck do I know. I guess we'd have to see a cowl hood like Shawns in a wind-tunnel test to see the real effect.

    Actually Shawn wanna be a guinea pig on this one? How about going to a toy store and getting one of those $1 toy planes with the wind-up plastic propellar, then taping it (without the rubber band) in such a way so you can position the prop in the middle of the cowl underneath it, and so you can see if from the drivers seat. Then go for a ride and see which way the prop spins?

    (I'm not really that interested in the results, but now I'm just curious as all hell!) [​IMG]

    BTW: here's a link I found to a site that has cowl bolt-on's and full cowl hoods. http://www.up22.com

    <font color=red>Steve88</font color=red>[​IMG]
    88K5 Silverado
    thunderdog@metallica.com
     
  15. Shawn

    Shawn 1/2 ton status Premium Member Author

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    I may do that and let you know.

    When you said "wind tunnel test", I was visualizing my tall K5 with 36" meats in a wind tunnel! Would be hilarious to see something like that. I wonder what the wind tunnel people would do if you brought in a lifted K5 like that??? Definitly wouldn't get good marks.

    Shawn
     
  16. Steve88

    Steve88 1/2 ton status

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    ...wouldn't be bad if it had a nose like those Daytona Charger's used to have! LOL !!!

    <font color=red>Steve88</font color=red>[​IMG]
    88K5 Silverado
    thunderdog@metallica.com
     
  17. RaisedK5

    RaisedK5 1/2 ton status

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    I'm no physicist, but from what i remember, the air as it hits the windshield creates a rolling high pressure system right at the base of the windshield, the faster, lower pressure air, jumps over this and up the windshield, this high pressure system, at higher speeds mind you, is what forces air into a cowl induction hood, so at lower speeds the cowl induction does little, its when you get a whole lot of air over the car that it makes a difference.

    RaisedK5

    "Friends don't let friends drive Fords"
     
  18. BurbinOR

    BurbinOR 3/4 ton status

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    Gotta agree with Shawn, my 71 SS 396 Camaro I put a non-functional cowl hood on to clear the intake and carb. I felt all kinds of heat coming into the passenger area of the car AFTER I put the hood on. No question about it, it was real, and not imagined.

    '79 - 406 w/IROC TPI - K5#5 - a <font color=orange>sickness[​IMG] <font color=blue>you never get enough of!! [​IMG]
     
  19. Eagle86K5

    Eagle86K5 1/2 ton status

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    They call high pressure high cause it is higher, low pressure is always below high pressure. It is this effect that causes a plane to leave the ground.High pressure flows over the wing and low pressure under the wing, the difference causes the wing to rise.
    Wind does come up from under the car, it also comes through the grill. For those who doubt this, how many times have you seen a Nascar take off for space? Listen to the announcers..."Well he got air under the car..." Now how is this possible? A car running 220 has a bunch of wind going over the top, and all the spoilers are forcing the car down on the track. High pressure on the top...low on the bottom.
    Used to be folks had scoops sticking right up in the way...Ram air they called it, then they got smart and turned it around, then reversed the scoop so it does not appear at all, again using Bernoullies principle,(from Comptons)

    Bernoulli's law, called the Bernoulli effect, states that an increase in the velocity of air reduces the static pressure. The Venturi tube of a carburetor illustrates this law. It is wide at each end but narrows in the middle. As moving air passes through the throat it speeds up and its static pressure decreases. The low static air pressure in the nozzle leading from the throat draws fuel into the tube from a bowl that is under normal atmospheric pressure.

    A wing in cross section is shaped like a side of a Venturi tube. Moving air has farther to go over its curved, or cambered, upper surface than over its flatter lower surface. The air moves more rapidly over the top than it does over the bottom and thus exerts less downward pressure. This pressure differential between the top and the bottom of the wing produces about 70 percent of its lift.

    See the attachment, as the air running through the carb sucks gas from the bowl, so does the air going over the top of the hood and windshield suck air from the engine compartment. The venturi effect is where the two meet at the back of the scoop , the faster high pressure air over the top sucks the lower pressure air from under the hood out over the windshield. Now what just happens to be in the way? The Intake....as the air is being directed by the scoop out it crosses over the intake of the carb, therby allowing it access to moving air, faster then if there was no scoop at all.
    If you will look up Venturi effect and Bernoullies principle in the encyclopedia you will understand just how this works.


    <font color=green>Eagle86K5[​IMG]

    <font color=red>Only guy I know that can get out of line in a one car funeral
     
  20. Steve88

    Steve88 1/2 ton status

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    Eagle, thanks bud, never had it explained that way. Here all along I've been thinking the "true" cowl hoods would grab the cold air from the top of the hood and direct it over the cowl and back-forward into the carb. I see your point though, but it still only makes sense (to me) in relation to non-true cowl hoods (which is what most of add-ons are going to be set up with anyway.)

    <font color=red>Steve88</font color=red>[​IMG]
    88K5 Silverado
    thunderdog@metallica.com
     

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