Carbs:Holley Vs. AFB

[Stuart F.]

Re: Carbs:Holley Vs. AFB

Bill;

Regarding the aerodynamics of the C-2's, I found the main problem to deal with before resistance at high speed is the "Reverse Wing" effect of the body. It is more inclined to fly than cut through the wind. It is very unstable at anywhere near 120 mph. My experience has been with the convertible body of my 63. Perhaps the coupe is better. My buddy and I made a series of high speed runs in Navada on our way to Vegas in 63 from New mexico on leave (of our senses too). I saw 150 on the speedo from the passenger seat at about 6200+ rpm. Now, these were readings taken while bouncing around and hanging on for dear life, and do not account for wheel slip or blurry vision. From the driver's seat, on another run, I was running steady 120 mph and noticed the dark clouds of a pending storm. So, I opened the headlights and noticed a big improvement in stability as the front seemed to pull down in, as we learned later, the inducement of downforce.

God bless the U.S. Royal Tire and Rubber Company for their 6.70 x 15 original equipment tires. I still have that spare tire (which will never touch the ground) to say a little prayer to now and then.

Stu Fox

[Clem Z.]

Re: Carbs:Holley Vs. AFB

Bill;

Regarding the aerodynamics of the C-2's, I found the main problem to deal with before resistance at high speed is the "Reverse Wing" effect of the body. It is more inclined to fly than cut through the wind. It is very unstable at anywhere near 120 mph. My experience has been with the convertible body of my 63. Perhaps the coupe is better. My buddy and I made a series of high speed runs in Navada on our way to Vegas in 63 from New mexico on leave (of our senses too). I saw 150 on the speedo from the passenger seat at about 6200+ rpm. Now, these were readings taken while bouncing around and hanging on for dear life, and do not account for wheel slip or blurry vision. From the driver's seat, on another run, I was running steady 120 mph and noticed the dark clouds of a pending storm. So, I opened the headlights and noticed a big improvement in stability as the front seemed to pull down in, as we learned later, the inducement of downforce.

God bless the U.S. Royal Tire and Rubber Company for their 6.70 x 15 original equipment tires. I still have that spare tire (which will never touch the ground) to say a little prayer to now and then.

Stu Fox

if GM had a wind tunnel back in those days they must have used it to dry the laundry because they did not use it on the mid years. putting a big block in a mid year help hold the front end down.

[Duke W.]

Re: Carbs:Holley Vs. AFB

I had my SWC up to 150 a couple of times. It's not really unstable, but you can tell that the front end is elevated and the steering gets light.

As long as there is no significant cross wind component and you only need to run in a straight line it probably feels a lot worse than it really is. It's not "unstable" - just sluggish.

A worst problem would be rear lift or the center of pressure ahead of the center of gravity, which could cause rear instablity. The latter might be more of a problem for the convertible model because it doesn't have as much side area rear bias as the Coupe.

Getting the center of pressure as far aft as possible is why some high speed race cars of the fifties had vertical tail fins. In fact, it's why airplanes have big vertical fins. Without them they would be completely unstable in yaw - like the B2, which would be totally unstable without the flight control computer constantly keeping it in line as a much higher frequency than any human can work at.

If any of you are old enough to remember the "dustbin" fairings on GP bikes back in the fifties - the fully enclosed front wheels - they placed the center of pressure so far forward that they were aerodyamically unstable, and after a number of crashes they were outlawed.

As far as the E-type is concerned, like so many other things automotive back then its performance was probably exaggerated, and if they did get one up to 150, I can believe it had a tweaked engine, but at the time I got into that little race I believed the propaganda.

Later I learned that US-bound E-types had a shorter axle ratio than European models, so their top speed - whatever it really was - was probably rev limited to well under what my 340 HP, CR 4-speed, 3.08 axle SWC could do.

That was the only time I ever got into a heads up race with an XKE. From that first experience I learned that they were too slow to even mess with anymore!

Duke

[Stuart F.]

Re: Carbs:Holley Vs. AFB

Never mixed wheels with an XKE. Just considered them something pretty to look at from England. Did they share "The Prince of Darkness" with their countrymen (Lucas that is)?? Come to think of it, I did punch it with a later E-Type V12 last year who was trying to beat me to a merge onto the 417 from a dual lane cash box. My main reason was self protection to get away from his putrid over rich smoke and that was no problem.

Stu Fox

[Clem Z.]

Re: Carbs:Holley Vs. AFB

Never mixed wheels with an XKE. Just considered them something pretty to look at from England. Did they share "The Prince of Darkness" with their countrymen (Lucas that is)?? Come to think of it, I did punch it with a later E-Type V12 last year who was trying to beat me to a merge onto the 417 from a dual lane cash box. My main reason was self protection to get away from his putrid over rich smoke and that was no problem.

Stu Fox

one on my biggest autocross competitors back in the day was "doc chain" in a XKE

[Duke W.]

Re: Carbs:Holley Vs. AFB

if GM had a wind tunnel back in those days they must have used it to dry the laundry because they did not use it on the mid years. putting a big block in a mid year help hold the front end down.

A 3/8-scale model of the Sting Ray Coupe was tested in the Cal Tech wind tunnel. AFAIK that may have been the first time a production car model was ever wind tunnel tested during the design process. It was a solid model and really too small and not sufficiently detailed to show the aero deficiencies of the design. There were pressure taps at various points and dye was also used to study surface flow.

The aero properties of high speed ground vehicles were not very well understood at the time.

Ford found that their GT-40 was well short of its projected 200 MPH top speed in early tests. They did not account for the drag power loss from the elaborate ducting of the complicated driver ventilcation system, which consumed about 50 HP near top speed. (When Shelby took over the program he ripped it all out.)

There was also an aerostability problem that cost Walt Hansgen his life. That was solved by redesigning the front end and adding the rear spoiler.

Duke