427 Cobra hood scoops

[my427cobra]

And, as a static tuft test, pics should be easy.

Cheers
Greg

[my427cobra]

In parallel to the tuft testing, and in anticipation of my hood scoop installation, I am going to begin taking temperature readings of various engine compartment components for a couple of months (as the summer gets warmer) before the scoop and then after the scoop is installed to see if there is any relative improvement.

So here attached is a copy of the temperature measurement chart I will use.

I'm going to use my Harbor Freight Infra Red digital thermometer for the readings.


If anyone has any suggestions to add for measurement points, let me know.

Cheers
Greg

[my427cobra]

Yeah I know. Engineers can't spell. LOL

Cheers
Greg

[Jdata]

So essentially the first test is primarily temperature readings with a subset of seeing what the vents are doing when the fans are engaged

[my427cobra]

Hi Jdata. Yup.

The static tuft test will at least visually tell me if the fans move air out of the fender wells/vents while the car is at a stop.

I know it does because as I said , while sitting in the driver's seat I can reach my hand forward and feel the hot air coming out the vent.

The temperature testing is more related to my plan to install a hood scoop in a month or so and see if the scoop contributes anything to cooling the top side of the motor.

I'm working on a couple of ideas to mount a camera to capture the tufts on the hood. Probably a camera mounted on the top center of the windshield frame.

And to capture the tufts at the vent, a camera mounted to an old wind wing that I have.

I'll use yellow yarn which should show up very well against my Rangoon Red paint color.


Cheers
Greg

[my427cobra]

News Flash: Tuft testing update!
I hadn’t really thought about doing any tuft testing quite so quickly, but it was a beautiful morning here on the central coast so I was headed to the Pismo Derelicts Saturday morning car show.

So yesterday I taped some yellow nylon string ( hereto : The Tufts) to the top inside of the side vents (that is inside the engine compartment, not on the outside of the fender).

Four tufts per side vent, one tuft per vent vane. I made the tufts about 6” long so they would be visible if blowing out the vent.

I did this initially to do a static (car at rest with the engine off) fan test to see if the puller fan on the engine side of the radiator would push the tufts out the vents.

It did but weakly.

So I fired up the engine and that’s what the fan needed. Amps.

The tufts now fluttered out the vents.

Here’s a pic of the tufts on the inside of the vents.

This morning I headed to the car show, only about a 10 min ride from my house and enjoyed a coffee and a chocolate buttermilk muffin. It’s important to keep your energy up during such critical testing.

After a couple of pleasant hours meeting with friends, car guys and looking at a lot of fine rides, I headed off on my usual 2 hour ride along the beaches , to land’s end at Avila Bay and through some winery canyons.

Then I remembered, the tufts were still taped inside the vents.

Well, I leaned out the driver’s side at about 45 or 50 mph and low and behold, the tufts cometh. They were waving at me as they fluttered out the vents and that was with no fan on.

Picture to prove it. Sadly , NO. For the moment you’ll have to take my word for it.

But yesterday I was experimenting as to how to take pics of the side vents.

My idea was to mount my digital camera or GoPro to an old wind wing and take pics that way. But the angle wasn’t right. And the camera mounted to the top center of the windshield frame wasn’t the right angle to take pics of the hood tufts once I mount my hood scoop.

So back to the drawing board, or beach as it turns out.

While driving back past the beaches on my way home this morning, I realized my problem.

I was thinking too old. The young kids on the beach were young.

And Eureka. I saw the solution: a SELFI STICK!!!!!!!!!!!

A selfie stick could be reached along the side of the car by a passenger to take a picture of the vent tufts while the car is moving, or by me on the driver’s side if I’m stupid enough. And once my hood scoop is on, a passenger can use a selfie stick to reach over the windshield and over the hood scoop inlet to take pics of the hood tufts.

Stay tuned.
Cheers
Greg

[my427cobra]

Crap. wrong pic

Greg

[cycleguy55]

I went for a brief drive today and realized shortly before hitting the highway that the hood wasn't latched. As an experiment I continued on. ~75 MPH and the hood stayed down - not even a wiggle.

If there was any pressure building up under there it would have lifted.

[strictlypersonl]

Originally Posted by cycleguy55

I went for a brief drive today and realized shortly before hitting the highway that the hood wasn't latched. As an experiment I continued on. ~75 MPH and the hood stayed down - not even a wiggle.

If there was any pressure building up under there it would have lifted.

When we raced an Austin Healey 100-4 (a similar shape to the Cobra) without a full windshield, we used loose leather belts at the rear. At speed, the rear would come up a couple of inches. The difference is that, with a windshield, high pressure extends forward enough to keep the hood down.

[Morris]

Also at 75 mph......you are not going fast enough to see how the Aerodynamics change when you approach the higher race speeds.

[cycleguy55]

Originally Posted by strictlypersonl

When we raced an Austin Healey 100-4 (a similar shape to the Cobra) without a full windshield, we used loose leather belts at the rear. At speed, the rear would come up a couple of inches. The difference is that, with a windshield, high pressure extends forward enough to keep the hood down.

I note the grille on the AH 100-4 is higher than is the opening on a Cobra. In addition the leading edge of the hood is higher and the hood itself has less front to rear slope on it than a Cobra hood. I'm not an aerodynamics expert, nor do I have access to a wind tunnel, but I believe the combined effect of these differences is quite significant.

Yes, the windshield pressure wave will affect the rear of the hood, but there are other factors at play.

[Jac Mac]

Originally Posted by my427cobra

Here's a pic of the Flip Top that I grabbed from Jac Mac's posting on the Shelby related pics thread.

CSX 2196 after a mid '90s restoration:


Good shot of the hood scoop.

Cheers
Greg

Greg, check your mail/inbox/junk mail folders, I sent several more pix of 2196 incl one taken from behind with hood up at same time as thefrontal view. that shows how underside of scoop services carb only.

[Anthony]

Originally Posted by Morris

Also at 75 mph......you are not going fast enough to see how the Aerodynamics change when you approach the higher race speeds.

Like what morris said.

Greg, you can drive @ 75mph, and stick your head out of the window, and then compare to driving at 150mph, and then sticking your head out of the window, and see if there's a big difference.

[cycleguy55]

Originally Posted by Anthony

Like what morris said.

Greg, you can drive @ 75mph, and stick your head out of the window, and then compare to driving at 150mph, and then sticking your head out of the window, and see if there's a big difference.

True, but the issue isn't whether there's an increase in velocity, resistance or force, the question is whether the airflow patterns change with velocity. Does laminar flow become turbulent at higher velocities?

Anyone have access to a wind tunnel?

[Morris]

Originally Posted by cycleguy55

True, but the issue isn't whether there's an increase in velocity, resistance or force, the question is whether the airflow patterns change with velocity. Does laminar flow become turbulent at higher velocities?

Anyone have access to a wind tunnel?

Yes.....

[Jac Mac]

If Greg (my427cobra) can get the pic I have to upload there are a couple of interesting points. On 2196 in what I assume are very early photos the Hood Scoop went thru quite a few design changes with hole to fit 4bbl sealed off or at least close fitting, 4x 58?mm webers etc with some appearing to use pressure from base of screen etc rather than hot air from engine bay.

[Blas]

While the tuffs of yarn were probably great at the time, I’m wondering if a remote temperature sensor would be the ultimate tool to check the direction of the air flow at speed thru the vents.
Blas