Air flow through hood scoop - Page 5

Bernica · #1 (**permalink**) 05-15-2008, 09:21 PM

I have CSX 4250. Just aquired it last week. All Shelby, including the stroked 582ci all-aluminum Shelby motor. Set up and has done road race (Willow Springs, Sears Point, Laguna Seca etc).
No hole in the hood at all and have a turkey pan w/ a race prepped 750 Holley. The guy I bought it from says Shelby doesn't cut to hood. It has a 1" AF that fits in the turkey pan. Kind of wondering what they are thinking? Any thoughts??? Has anyone cut their hood on a CSX4000???

Rick Parker · #2 (**permalink**) 05-15-2008, 09:56 PM

With the low hood clearance and relatively this air filters that all the 427 FE folks seem to be stuck with, the best thing to do would be remove the choke housing on the Holley and radius all incoming corners. There is a reason you don't see a choke housing on a Race Carb....air flow.

Double Venom · #3 (**permalink**) 05-16-2008, 04:28 AM

Sorry to come in so late on this, but we did do as much testing without a tunnel as we could. (2000 ?) The difference was amazing. We did use the yarn tufts, video taped at 30-50-70 and 100mph. Tufts were installed in the very front of the "Naca Duct" much like a Viper uses and on top of the Naca Duct. Tufts were installed in the very front of the rearward facing scoop, along the top and at the very back. Just for giggles we installed tufts about 4" apart on the lower windshield, the middle of the windshield and of course at the top.
What we found was amazing and good info. The tufts in front of the Naca Duct actually were sucked inward while the top tufts almost didn't move. The tufts at the rear of the scoop actually got totally sucked into the engine comparment ALONG with the tufts at the lower windshield area. The middle windshield tufts couldn't makle up there minds to go up or down into the intake. The upper tufts finally went up. The reduction of air pressure on the windshield was amazing in itself.

Bottom line, want more air into the intake with positive pressure and not a vaccum, turn the scoop around and no need to raise it higher.

Maybe the Kirkham group had something going there

DV

Mother · #4 (**permalink**) 10-23-2008, 01:27 PM

Turn the scoop around... Humm. I aam going to use the Classic Dynatek Direct induction system on my build. (mild 351W w/ 435 // 430 ft) The system would benifit from the reverse scoop with the use of a turkey pan. Hummmmm.
Mother

Mother · #5 (**permalink**) 10-23-2008, 01:31 PM

Double Venum
Nice use of "Duponts Croman Illision" on the build. I have no concerns about changing the looks of the hood to an improved air flow question.

DougD · #6 (**permalink**) 10-24-2008, 08:42 AM

Has anyone tried adding vents to the hood? If the air coming through the radiator is causing air to flow out the scoop, what if we gave the air another place to go?

Michael C Henry · #7 (**permalink**) 05-16-2008, 09:36 AM

This information would have helped Shelby 40 years ago.. But he probably would argue that wouldn't have made any difference or that the technology would have not remained a secrete for long. There are resons for departing from some of the traditional body arrangements. My car is a replica and WA registertraion says KitV first . A cowl induction scoop would help my situation. Now to find a cowl scoop that would look appropriate on a Cobra hood. I'm up to bonding but a new layup seems intimidating. I'd Like to get all this done before getting car repainted. I know a change is neccessary and a scoop would be step to an end. Do you remember reading anewbie asking what you do once the Cobra replica is finished?
How or what did you come up with the rear edge ? Did the rear of the scoop follow the windsheid or end at the hood line edge or does the top extend over and open on sides.? What is the optimum shape?

Double Venom · #8 (**permalink**) 05-16-2008, 10:43 AM

Michael,
If you didn't know, it is a CR's Cobra. All I did was cut out the original scoop, turn it around and fiinished it from there.
DV

Ant · #9 (**permalink**) 05-16-2008, 04:33 PM

I have decided to bypass an original looking forward scoop and have a rear facing scoop, due to my scoop being quite high. Will be going to the hood edge which is about 6-7" away from the windscreen. The windscreen is going to be the original but am making a small 9" high polycarbonate screen that goes right across, so not sure on the air effect in that area, but for looks its 1000% better!

I think 6-7" is okay from the rear of scoop to screen to pick up air. To my way of thinking unless its an original scoop anything larger than that is just plain ugly.

Another bigger issue is the air filter, and I cant see the point in oval and small air filters, the oval dropped filters restrict in the side entry to carb, I have now a proper 14" setup, which makes the scoop a bit wider, and just have room for a 4" high air filter which has >2.5" above the carb flange!

Badger · #10 (**permalink**) 10-23-2008, 12:28 PM

Dave....You are on the right path my friend. Simple evaluation of basic airflow is something most Snake owners don't ever consider. They are so obsessed with being "original" that any change is considered heresy. You might install a set of air/fuel ratio gauges in your pipes to start with. A simple change you might try is to reverse the direction of the hood scoop. There's more air pressure at the base of the windscreen than out on the middle of the hood's surface. (a simple manometer test will prove that) Don't be afraid to go against the majority's opinions....there's little knowledge there..only monkey see monkey do. Badger

davids2toys · #11 (**permalink**) 10-23-2008, 01:14 PM

Quote:

Originally Posted by Badger

Dave....You are on the right path my friend. Simple evaluation of basic airflow is something most Snake owners don't ever consider. They are so obsessed with being "original" that any change is considered heresy. You might install a set of air/fuel ratio gauges in your pipes to start with. A simple change you might try is to reverse the direction of the hood scoop. There's more air pressure at the base of the windscreen than out on the middle of the hood's surface. (a simple manometer test will prove that) Don't be afraid to go against the majority's opinions....there's little knowledge there..only monkey see monkey do. Badger

Thanks Badger, but I probably fall into the same crowd, sort of anyway!
I still want it to look very Cobra-ish, I have no interest in turning the scoop around, and I am a working JOE so everything needs to be cost effective.
I figure, if I can at least supply lots of air availability(ducts), CFM availability( much bigger air cleaner), Looks( ducting, cobra oval AC dropped down to accept a 3" element, modified turkey pan or airbox).../then I will have a much improved performing car, and still look great at the car shows and for my own eye!

JBCOBRA · #12 (**permalink**) 10-23-2008, 01:19 PM

Hi Lew!
Your car is Sweet!

JBCOBRA · #13 (**permalink**) 10-23-2008, 01:30 PM

About the only thing my hood scoop does, that I can think of is: allow clearance, and let heat out when you turn off the car. I tried the yarn on the scoop trick, and the big opening in the front of the car was just forcing hot air out of the scoop while driving. LOL

petercory · #14 (**permalink**) 10-24-2008, 11:30 AM

The Problem is the Turkey Pan, with it on, the scoop cant flow enough air for a 500CFM much less a 750 or 780CFM Carb! Do a full bore accceleration run and shut the key off at about 6000RPM and take a plug reading - They'll be black with the pan on. Take the Turkey pan off and do the run again - if the carb is jetted properly, the plugs will read perfectly! We proved this out while tuning for a Run & Gun many years ago.

davids2toys · #15 (**permalink**) 10-24-2008, 02:37 PM

Quote:

Originally Posted by petercory

The Problem is the Turkey Pan, with it on, the scoop cant flow enough air for a 500CFM much less a 750 or 780CFM Carb! Do a full bore accceleration run and shut the key off at about 6000RPM and take a plug reading - They'll be black with the pan on. Take the Turkey pan off and do the run again - if the carb is jetted properly, the plugs will read perfectly! We proved this out while tuning for a Run & Gun many years ago.

Also, if the filter element can only flow 470 cfm(mine)

dls141 · #16 (**permalink**) 01-04-2012, 02:38 PM

Quote:

Originally Posted by petercory

The Problem is the Turkey Pan, with it on, the scoop cant flow enough air for a 500CFM much less a 750 or 780CFM Carb! Do a full bore accceleration run and shut the key off at about 6000RPM and take a plug reading - They'll be black with the pan on. Take the Turkey pan off and do the run again - if the carb is jetted properly, the plugs will read perfectly! We proved this out while tuning for a Run & Gun many years ago.

So you're saying if I'm running an 850cfm holley on a 427 so I should take the turkey pan off.

Dwight · #17 (**permalink**) 01-04-2012, 06:33 PM

dls141

notice this thread started in Feb 2004 and stayed active till 2008. Lots of good info in this thread.

The turkey pan is killing your hp.

I did the cal's on an 8" S&S air filter on a 351W with 400 flywheel hp. At 4000 rpms it was losing 97 hp because of the filter.

use this link to cal your air filter. You can not get the proper size filter in the turkey pan.

Second Strike Air Cleaner Calculator

Dwight

dls141 · #18 (**permalink**) 01-06-2012, 11:35 AM

Quote:

Originally Posted by Dwight

dls141

notice this thread started in Feb 2004 and stayed active till 2008. Lots of good info in this thread.

The turkey pan is killing your hp.

I did the cal's on an 8" S&S air filter on a 351W with 400 flywheel hp. At 4000 rpms it was losing 97 hp because of the filter.

use this link to cal your air filter. You can not get the proper size filter in the turkey pan.

Second Strike Air Cleaner Calculator

Dwight

Thanks Dwight. I've seen the TP setup before on a small block but thought it looked odd - and constricting on the 427.

We'll be installing the new Holley next weekend and I'm dropping the turkey pan. It's great to live 30 minutes from Summitt too!

mr0077 · #19 (**permalink**) 01-05-2012, 09:43 AM

G-Pete, I thought I posted some "real-world" results on this thread early-on, but maybe not. Here you go:

I have a mild 2x4 sideoiler with 2 600 CFM Holleys. The guys in Houston all decide to do a "dyno day". I put mine on it, did two back-to-back pulls and got 394 RWHP with stock paper filters on the S&H housings, and 402 RWHP with just the base of the S&H housings on the carbs (I've been told that without the base of the housing the airflow into the carb gets disrupted).

That makes 7 RWHP difference between paper elements and no elements, up through 5500 RPM. The reason I run paper elements is because the K&N elements let way more fine particles through, and for 7 HP, it isn't worth it.

Now for the guys with one big carb, the single S&H filter seems way too small, but for me, it works. And FWIW, Double Venom's tuft work confirms what I had always suspected, the hood scoop is good looking, but fairly worthless, and any benefit you'd get from cool air by sealing your carb to the hood would be lost by starving the engine for air (at higher RPM). JMHO.

olddog · #20 (**permalink**) 01-08-2012, 09:17 AM

Quote:

Originally Posted by mr0077

And FWIW, Double Venom's tuft work confirms what I had always suspected, the hood scoop is good looking, but fairly worthless, and any benefit you'd get from cool air by sealing your carb to the hood would be lost by starving the engine for air (at higher RPM). JMHO.

Is the restriction the small air filter you are forced to use by the turkey pan or the scoop?