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Old 03-29-2019, 02:35 PM
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Default 427 Cobra hood scoops

Hi all. I have a two part question about 427 Cobra hood scoops:

Part 1: I have a 427 Cobra hood scoop that I purchased about 20 years ago at a SAAC convention:







Yes that is an original Shelby autograph.

The hood scoop is 17" wide x 24" long including a 1" flange. The scoop opening is 15" wide x 1.5" high. The front opening has a 0.5" flange folded over to the inside along the top edge of the opening.

Is this a "correct" hood scoop? Shape? Size?

What application is it for? S/C? Comp? Webers?

Is this scoop still available from some source?

Part 2: Do these scoops feed enough air to aid in cooling on a street car application?

I do not have an engine cooling problem as I have a sufficiently sized aluminum radiator and two sets ("period correct" fans ahead of the radiator and a large shrouded puller fan behind the radiator) of fans to cool it. With the fans operating I can cool the water temp below 185 deg F on an 90 deg F day in stop and go traffic. So I don't have a cooling problem.

But I think i have had occasional vapor lock problems with all that hot air under the hood and would like to reduce underhood temps.

Would a hood scoop help by moving more air into the engine compartment while moving or moving more air out while stopped?

Now here is some heresy. Would cutting out an opening in the back of the scoop aid in suction effect to pull hot air or allow the fans to push more hot air out? Yes, some hot air may spill over the windshield into the cockpit.

Just wondering.

Cheers
Greg
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Old 03-29-2019, 02:46 PM
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Original scoops alloy? Lol

Last edited by 1985 CCX; 05-02-2019 at 03:12 PM..
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Old 03-29-2019, 02:55 PM
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A scoop like on Cobras will actually have air pushing out from the engine bay at speed.

There is much more surface area in the nose than the scoop. Thus more air pressure pushing in the radiator than in the scoop.

If you have a turkey pan or some other method to seal to the bottom of the hood, then the hood scoop will do what you think it should. There is no opposing air pressure in this situation.

Most of the OEM muscle cars had air boxes that sealed to the hood.

John
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Old 03-29-2019, 03:53 PM
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Yes 1985 CSX, I believe the original scoops were aluminum and riveted to the hood. My question is whether this is the "correct" shape and size.

Thanks Grubby: Thanks and you've pretty much answered my question, as my thoughts were about hot air flow exiting the engine compartment rather than sealing a turkey pan like cold air box for the carbs.

Cheers
Greg
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Old 03-29-2019, 04:17 PM
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I think the hood scoops on the 427 cars (csx3k) were fiberglass.
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Old 03-29-2019, 05:19 PM
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the scoops were fiberglass on all the original 3000 series original cars i have seen.
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Old 03-29-2019, 08:36 PM
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I would just put that on your wall.
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Old 03-30-2019, 09:12 AM
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Yep, original scoops were fiberglass.
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Old 03-30-2019, 02:39 PM
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Quote:
Originally Posted by cobrakiwi View Post
I think the hood scoops on the 427 cars (csx3k) were fiberglass.
That was my understanding as well. Same scoop as Mustang GT350s?
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Old 03-30-2019, 02:47 PM
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Quote:
Originally Posted by Grubby View Post
A scoop like on Cobras will actually have air pushing out from the engine bay at speed.

There is much more surface area in the nose than the scoop. Thus more air pressure pushing in the radiator than in the scoop.
Sorry, that myth is refuted by this video: https://www.youtube.com/watch?v=XFdkLFvqbZY

Worth noting is the surface area around the bottom and sides of the engine compartment are far greater than the combined area of the radiator opening and hood scoop. It is therefore easier for air to exit under the car and through the wheel wells and side vents than it is for it to exit through the hood scoop - though that may be different when idling in traffic.
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Old 03-30-2019, 05:47 PM
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Quote:
Originally Posted by cycleguy55 View Post
That was my understanding as well. Same scoop as Mustang GT350s?
The Shelby GT350 hood scoop is entirely differed than the one depicted in the original posting, just a FYI.
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Old 03-30-2019, 05:52 PM
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Depending on the brand Cobra you have, some will let more air in through the nose than others. Anyone know what kind was in the video?
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Old 03-30-2019, 06:08 PM
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The hood scope is all about getting cooler fresh air into the intake (carb) for combustion. But without something directing the cool air into carb or throttle body, it will just add to air flow down into the engine bay and under the car without any real benefit for a cold air charge. When I was working with heat exchanger design for turbos, the capture of the cool air was almost as important as the heat exchanger's thermal transfer capability.

If you add a turkey pan around the carb and have a good hood scoop, it will most likely reduce, if not eliminate, your vapor lock. I think I remember some posting on this site in the past describing people even adding some shielding on the bottom of the turkey pans to better insulate the heat coming up from the top of the intake manifold to the bottom of the carb body. This is the heat that causes the fuel to vaporize the fuel right in the carb before it really gets to enter the intake runners.

The incoming air at speed will only flow as the intake throttle sucks air and the additional leakage around the pan and the bottom of the hood. If you look closely at the Mustang Shaker style scoops and Chrysler's intake scoops, they are sealed to the air cleaner and typically not very large for the opening.

I will be interested in some of the experts on here helping to identify the scoop you have!

Good Luck!
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Old 04-05-2019, 03:43 PM
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Quote:
Originally Posted by Grubby View Post
A scoop like on Cobras will actually have air pushing out from the engine bay at speed.

There is much more surface area in the nose than the scoop. Thus more air pressure pushing in the radiator than in the scoop.

If you have a turkey pan or some other method to seal to the bottom of the hood, then the hood scoop will do what you think it should. There is no opposing air pressure in this situation.

Most of the OEM muscle cars had air boxes that sealed to the hood.

John
I just think thatís unlikely. This would only be the case if the engine bay were sealed, the only apertures were the grille and hood scoop. In fact the bay is totally open and the air passes in through both and out under the car and transmission tunnel. However, it may be that it causes turbulence in the engine bay and that would be a good research exercise.
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Old 04-06-2019, 12:52 PM
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is your fuel pressure regulator setup with a return line? it will keep cool gas always flowing the lines so the fuel does not heat up in the lines. That will fix your vapor lock problem if that is what it really is.
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Old 04-08-2019, 08:54 AM
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Great discussion on this subject. Thanks for all your input.

But, I'm still trying to determine the genesis of the aluminum hood scoop I have.

I have found many fiberglass hood scoops from numerous sources but they are an inch or two narrower than my scoop and quite a bit "squarer" at the back of the scoop while mine is somewhat tapered and more round at the back.

Not sure which are the "original" dimensions and shapes.

I also thought I had read somewhere that there were two widths of hood scoops for the 427 Cobra with the big 58mm Weber carbs using the wider scoop?

Cheers
Greg
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Old 04-08-2019, 09:16 AM
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These pics show the difference in the hood scoops.

My aluminum scoop that is 2 inches wider, more tapered and rounder at the back:



And two fiberglass hood scoops available in the market place:





Quite a difference in shape.

Cheers
Greg
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Old 04-09-2019, 09:45 AM
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The only way a hood scoop lets purely cold are in is if the scoop has a sealed base. Period. The opening in the front of the car is 20 times bigger, forcing some air Out of the hood scoop.
Have you ever driven a Cobra that does not have a sealed base in the rain? Open the hood and look at the engine/distributor afterwards. The engine will be dry.
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Old 04-09-2019, 11:40 AM
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Quote:
Originally Posted by JBCOBRA View Post
The only way a hood scoop lets purely cold are in is if the scoop has a sealed base. Period. The opening in the front of the car is 20 times bigger, forcing some air Out of the hood scoop.
Have you ever driven a Cobra that does not have a sealed base in the rain? Open the hood and look at the engine/distributor afterwards. The engine will be dry.
Your theory would work if the engine compartment was sealed - but it's open on the bottom and sides.

Have you watched the yarn in this video?: https://www.youtube.com/watch?v=XFdkLFvqbZY

The strands clearly indicate the air is flowing IN the hood scoop, not out. Feel free to shoot your own video showing otherwise and post a link to it.
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Old 04-09-2019, 02:48 PM
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Something I've not seen mentioned here is the Venturi effect of air rushing under the car and buy the side vents. this. This by itself should be enough to expel any are taken in through the intake ahead of the radiator and through the hood scoop.
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