427 Cobra hood scoops

[Jdata]

I am not completely sold on that video. I wonder if you put the strings in front of the hood scoop instead of laying down onto it... I would like to see the air moving in front of the scoop. the issue I have is the front of the car isn't exactly great I am concerned with turbulent air due to the shape of the front of the car. I'm looking at the boundary layer. The Dodge can't have to use a higher scoop to grab air, the scoop on a cobra is barely 2 in tall.

I do believe that the intake has to be sealed to get cool air

[t walgamuth]

yes to be the best it can be. But that should be a high pressure point and should have air coming in I would think and make it cooler around the intake even without a sealed turkey pan.

[cycleguy55]

Originally Posted by Jdata

I am not completely sold on that video. I wonder if you put the strings in front of the hood scoop instead of laying down onto it... I would like to see the air moving in front of the scoop. the issue I have is the front of the car isn't exactly great I am concerned with turbulent air due to the shape of the front of the car. I'm looking at the boundary layer. The Dodge can't have to use a higher scoop to grab air, the scoop on a cobra is barely 2 in tall.

I do believe that the intake has to be sealed to get cool air

There's no reason you couldn't put yarn strands on top and bottom. Shoot the video and let us know what you find out.

[my427cobra]

Love the free expression of knowledge, experience and opinions here.

So much to learn!

Well cycleguy55. Are you up to another "double tuft test"?

Cheers
Greg

[cycleguy55]

Originally Posted by my427cobra

Love the free expression of knowledge, experience and opinions here.

So much to learn!

Well cycleguy55. Are you up to another "double tuft test"?

Cheers
Greg

I will when: a) the car is running; and b) when I figure out how to mount the camera to get the shot.

[saltshaker]

Anyone put thought to the scoop causing a vacuum on the carb at higher speeds?
Jon

[Jdata]

Originally Posted by cycleguy55

I will when: a) the car is running; and b) when I figure out how to mount the camera to get the shot.

Thank you for doing this!

GoPro suction mount?

[Dwight]

What happens at 120 mph?

Does the scoop work at those speeds?

[saltshaker]

I’ve been on the track several times and in 3rd gear I hit a wall around 5k
Motor was dyno’d At 500hp @6k...I added a electric pump behind the mech and it pulls strong to 5400... so I’m wondering if the scoop is causing a vacuum effect?? I’m going to try running with out the air filter and closing the scoop and see if the corrects the problem. I have had the car up to 125mph but taking it up there slower
Jon

[cycleguy55]

Originally Posted by saltshaker

I’ve been on the track several times and in 3rd gear I hit a wall around 5k
Motor was dyno’d At 500hp @6k...I added a electric pump behind the mech and it pulls strong to 5400... so I’m wondering if the scoop is causing a vacuum effect?? I’m going to try running with out the air filter and closing the scoop and see if the corrects the problem. I have had the car up to 125mph but taking it up there slower
Jon

Was it dyno'd with the same configuration that's installed in the car, including the same air filter, fuel pump and exhaust system? It's unlikely it was dyno'd w/o mufflers or other restriction, and entirely possible it was dyno'd w/o the air cleaner - meaning your problem may have absolutely nothing to do with the scoop.

Regardless, if you're trying to isolate a problem you'll be working at cross-purposes if you change more than one thing at a time. I wouldn't want to run an open scoop without an air filter, so I'd start by leaving the air filter on and blocking off the scoop. If that makes a difference, then great. If not, the next try is with the air cleaner removed.


Good luck in tracking it down!

[saltshaker]

It was dyno’d with out the second fuel pump. Adding a electric pump to get the fuel to the mech pump helped but not enough...I’m going to try it with out the air filter, the with the scoop closed....
Jon

[my427cobra]

Earlier in the thread Grubby said this:
“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.”

I’d like to talk a little about Grubby’s assertion and separate the two elements:
1) area of the Cobra nose opening/radiator measured in square inches
2) pressure/air flow due to forward movement or fans
The area of the Cobra’s elliptical nose opening is approx. 225 sq in.
My aluminum radiator finned area is 330 sq in.
But a typical radiator only has 33% effective open area which equals 110 sq in.
(forgetting for a moment air friction and turbulence as the air moves through the fins)
But in front of my radiator I also have two fan motors and two five bladed fans all totaling 140 sq in of obstruction. (forgetting about the splitter and oil cooler fittings and hoses protruding into the opening)
So I actually have more obstruction area than radiator effective open area.
So lets spin the fan blades to create air flow/pressure and zero out the obstructive area for the blades.
Net net I have 205 sq in of nose opening trying to pass air through 110 sq in of radiator effective open area.
Now a typical electric puller fan (let’s say a fan rated at 1800cfm if you have sufficient voltage and your wiring/relay are rated correctly) has a 33% efficiency drop thru a 2 core 1.5” radiator (55% loss thru 3 and 4 core radiators).
Now you’re depending on the fan at low vehicle speed to supplement air movement through the radiator vs air movement through the radiator at higher vehicle speeds.
So where is all this air going?
The side vents amount to 80 sq in and the area in front and around the side of the engine amount to another 200 0r 300 sq in. So there is a lot of room for air to exit.

Now, I can imagine with a car standing still, and in the absence of the venturi effect of air moving under the car in motion and drawing air out of the engine compartment, and with the fans running, air could be coming out of the hood scoop opening.
If I’m sitting at a stop with the fan running and I reach forward on the side of the car towards the side vents, I certainly can feel a lot of hot air coming out.
And if I reach down the side of the car towards the ground (my car is a street version – no side pipes) there is a lot of hot air exiting from under the car.
So there is a lot of air movement out of the engine compartment when stopped.
The air movement into or out of a hood scoop?
Well my thoughts are this: the hood scoop opening is 17 in x 2 in which equals 34 sq in. Keeping in mind the radiator only has 110 sq in of effective open area so the hood scoop adds 33% to the air entering the engine compartment.
On top of that, the air entering the hood scoop is at ambient, let’s say 75 deg, while the air coming through the radiator has been heated to, let’s say 185 deg.
So a hood scoop will be dumping 33% more air into the engine compartment at a much cooler temp.
That’s why a turkey pan works.
Now my car is a street version with two 4bbls and no turkey pan/cold air box.
So all that cooler air will be bathing the carbs and top of the engine in cooler air as the car is moving
So until I get a hood scoop on the car and do a tuft test, I won’t know how effective it will be.
My guess is it’ll work just fine.
Stay tuned.
Cheers
Greg

[my427cobra]

So how does any of this answer my question as to the genesis of my aluminum hood scoop?


Well, after looking at hundreds of pictures and not seeing anything like the aluminum scoop I have, I stumbled upon a picture of Ken Miles’ Flip Top/TheTurd Cobra. I had always seen, or rather focused, on pictures of The Turd racing at Nassau, in its as raced configuration, which had a hood scoop similar to those on other racing Cobras of the time.


But then I saw it. A couple of pictures of The Turd prototype, just after built and being readied for testing at Riverside in Sept ’64.


A special alloy block 390 with Webers had been fitted into the 289 chassis with the famous Flip- Top light gauge body. But the engine was a leeetle too big. So a large bubble/hump was added to the hood to accommodate the higher profile 390. It was not a scoop, just a big hump.
But, by the time The Turd raced at Nassau three months later , the hump had disappeared and was replaced with a hood scoop similar to those on other racing Cobras.
So why was the original hump so big when a “standard” Cobra scoop was eventually fitted and cleared the top of the Webers just fine?
Don’t know.
But, THAT SHAPE!
It closely resembles the shape of the aluminum hood scoop I have. It’s as if someone took that prototype hood bubble/hump, cut it back about 6 inches at the front, and created an air inlet.

Resulting in a wide, curved hood scoop. (Please excuse my amateurish photo-shop)


Looking a lot like the one I have:


Now I’m not saying I have the bubble/hump/hood scoop from The Turd.
I highly doubt it is even related.
But the aluminum hood scoop I have is very similar in shape and size and I have not seen anything else like it after looking at hundreds of period photos.
So what do I have?
Your guess is as good as mine.
But I like it!
I am now contemplating taking a splash off the scoop and making a couple of fiberglass reproductions. I may even mount one on my car.
Stay tuned. And then the “tuft test”.
Cheers
Greg

[t walgamuth]

I like the body on the Turd better than the 427 they built. Wonder why they went with what they did? More parts from the 289 usable? Front fenders, main body? I would also prefer the front and back wheels being even or narrower in back.

[Anthony]

I think the Turd had a wider scoop to accommodate the 58 Webers on the 390FE. ? aluminum HiRiser heads ?

[my427cobra]

Hi Anthony. You are right about the hood bubble. It was necessary to clear the big Webers 58's.

But, the hood bubble was on The Turd prototype in Sept '64 but was replaced by a hood scoop by the time the car appeared at Nassau in Dec '64.

So what changed? Did the special alloy 390 change from big Webers to a 4bbl when it raced at Nassau?

Cheers
Greg

[1985 CCX]

Guys
Original scoops were glass.

3002

[1985 CCX]

The Turd had many changes over the time it was being run as it was a trial and error car. Today it carries std scoop.
Guessing it has for decades.

If you like your scoop, use it.
Will set you apart from others. I like it, almost put identical scoop on my CCX years back.
These used to be a regular item on eBay. From recollection around 2005-2008 ish.
At one point I had two, think I still have one around somewhere

[Anthony]

It's hard to tell, but I acftually installed that larger scoop on my cobra. Bought it from cobra restorer's ?15 years ago? They called it the "weber" scoop.



Also, here is the comparison of the 58mm Weber intake for High Riser heads, that I think was used on the Turd, next to a 48 IDA intake.

[my427cobra]

Beautiful car Anthony.

I think my hood scoop is a little wider and more curvaceous than the one
pictured on your car.







But I have all my old (back to the '90s) Cobra restorers cataloges so I'll dig them up and look.

Great pics of those manifolds. Are they in your collection?

Cheers
Greg