Air Dam for my new Scoop

[Mike Gaines]

---
Never tried reducing the hood opening. Being the first year for both the car and myself, the hood opening was not even a thought. It was obvious that the scoop was grabbing huge air though, most noticeable towards the end of the pass.

I am going to figure out how to make my scoop width opening smaller.
Doesn't need to be that wide.
I needed the 5.25 inch HEIGHT to allow room for my dominator and very tall INDY intake and 1" open spacer....but...I don't need the width...I drilled several 1/2 inch holes in the rear corners of the scoop to let air pass thru the scoop on each side of the carb.
I did run my fastest ET ever (10.158) with this scoop the way it is configured now with the big wide opening.
Also I video all the runs with my helmet mounted go pro and did not see the scoop or hood wanting to lift at 131+mph..but if it catches less air I might go 10.157...lol



PS: If you look above the carb you will see where I installed a 18" square sheet of aluminum so in case the motor backfired and had a little fire going in the carb it would not allow the flame to hit the underside of the fiberglass scoop directly

 

[malex]

I am going to figure out how to make my scoop width opening smaller.
Doesn't need to that wide.
I needed the 5.25 inch HEIGHT to allow room for my dominator and very tall INDY intake and 1" open spacer....but...I don't need the width...I drilled several 1/2 inch holes in the rear corners of the scoop to let air pass thru the scoop on each side of the carb.
I did run my fastest ET ever (10.158) with this scoop the way it is configured now with the big wide opening.
Also I video all the runs with my helmet mounted go pro and did not see the scoop or hood wanting to lift at 131+mph..but if it catches less air I might go 10.157...lol

View attachment 587934

PS: If you look above the carb you will see where I installed a 18" square sheet of aluminum so in case the motor backfired and had a little fire going in the carb it would not allow the flame to hit the underside of the fiberglass scoop directly

---
Good idea Mike, it would be easy to fab up an aluminum filler at your scoop opening with a reduced opening.

 

[Mike Gaines]

---
Good idea Mike, it would be easy to fab up an aluminum filler at your scoop opening with a reduced opening.

I will post pictures of what I will have done when I am finished.

 

[FLY 9999]

Many of the examples of air flow diverters posted, work well when you want to achieve the most power, ET and MPH. They don't always work so well when you need to run a specific number like a dial in. Anything that causes the air to be turbulent causes pressure changes in the carb itself and will give an erratic ET. Playing around with '68 Hemi scoops, early pro stock scoops and presently '67 RO scoops(the tall one) over the years with BB,Hemi and SB, I've found that the K&N 4" filter produces the best HP and consistent time slips. My ET and MPH improve when I take the hood of and just run the filter(food for thought). A few friends have made .07-.15 gains in removing the Hilborn style scoops from their single 1050 combos to the 8' K&N stack and filter. The K&N extreme lid-filter top works better than the lid filter plus the round filter(regardless of height of the filter). They don't look as good as a raw scoop/carb combo that we have all seen but the 4" filter works the best. You can have a carb shop dial in your car/carb/scoop combo to best flow but this does costs several hundreds of dollars. Warren Johnson did research for K&N and the pro stock scoops. It took a lot of power to produce the power gains he felt were acceptable. Remember that these cars are running 200+ MPH and scoops begin to work after 150 MPH.

 

[gtxracer]

Made me google it.
http://www.intensityracingproducts.com/shop/pro-series-screens/

Fran, this screen top only keeps out the big stuff or bug stuff, me thinks!
Bob

 

[Fran Blacker]

Fran, this screen top only keeps out the big stuff or bug stuff, me thinks!
Bob

Like the product. What's that ol' saying "Stick and Stones may break.....)

 

[Endangered Species]

Mine has no holes in the back of the scoop. Flat pan with foam sealing against the hood. 5" Hemi scoop. Hood is held on with 4 hood pins. Has never come off. 500 passes at 145+. I will say I wouldn't run holes in the back of the scoop without a baffle like the one pictured. I have tested and found the air blowing over the carb will lower the pressure above the bowl vents. This WILL lean the mixture. Run with no hood and see the fuel mist up on the windshield at the end of the run. For what it's worth;
During testing the turbo car with blow thru carb to get correct A/F ratio we kept adding jet. Then we installed 90 degree spark plug boots over the bowl vents facing forward into the air stream. The same A/F required jets 10 sizes smaller.
Doug

Doug,

This is interesting. Tell me if I'm thinking right.
So the air flowing over the carb is creating turbulence then it has trouble pulling the fuel through the system causing leaning out of the mixture.... kind of like having too large of a intake plenum.

By putting the boots facing the air stream it's making the carb go lean by pressurizing the carb and forcing the fuel into the air stream.

So which way was faster?

 

[dvw]

Doug,

This is interesting. Tell me if I'm thinking right.
So the air flowing over the carb is creating turbulence then it has trouble pulling the fuel through the system causing leaning out of the mixture.... kind of like having too large of a intake plenum.

By putting the boots facing the air stream it's making the carb go lean by pressurizing the carb and forcing the fuel into the air stream.

So which way was faster?

The tubes definitely helped. My feeling is air blowing over the top of the bowl vents lowers the pressure differential between the top of the fuel column in the bowls and the booster. This lessens fuel flow with the same amount of air through the throttle bore leaning the mixture.
Doug

 

[Mike Gaines]

DVW...so, point the 90 degree plug boots forward or backward ?

 

[Endangered Species]

Thanks Doug... I can see what your saying, I'm going to try it.

Mike...He's saying forward into the Windstream.

Thanks guys.

 

[Deleted member 27881]

Hi guys, I really like this thread, great info. I'm going to build a cowl induction hood system and after reading your information I'd like to add an air dam to it for my 1968 Dodge Charger Build. I drew this up last year and am hoping to make it this year. Any suggestions would be great. Again awesome information. Thanks -Joel

 

[Mike Gaines]

Hi guys, I really like this thread, great info. I'm going to build a cowl induction hood system and after reading your information I'd like to add an air dam to it for my 1968 Dodge Charger Build. I drew this up last year and am hoping to make it this year. Any suggestions would be great. Again awesome information. Thanks -Joel

View attachment 591736

?????????????????????

 

[Deleted member 27881]

?????????????????????

I'll draw up a hard-line drawing to scale of the sketch with labels and part ideas.
It's suppose to be a section at the top of the motor at the air filter, carb, hood & scoop.

 

[LemonWedge]

Mike, going back to your air dam you fabbed: you currently show it mounted on the back side of the carb, essentially scooping air into the venturies. I wonder if it wouldn’t be MORE effective if mounted 180 degrees, on the front of the carb (?). Up front it may block turbulent air and create a low pressure point behind it allowing less turbulent air to enter the carb, instead of potentially more turbulent air rushing in from in front. (????).

 

[Mike Gaines]

Mike, going back to your air dam you fabbed: you currently show it mounted on the back side of the carb, essentially scooping air into the venturies. I wonder if it wouldn’t be MORE effective if mounted 180 degrees, on the front of the carb (?). Up front it may block turbulent air and create a low pressure point behind it allowing less turbulent air to enter the carb, instead of potentially more turbulent air rushing in from in front. (????).

I can't buy into that theory. Sorry.

 

[glassman]

How did the pro stock teams do their scoops when running carbs. This stuff has been hashed out before. Look at the winning teams.

 

[not so famous bob]

How did the pro stock teams do their scoops when running carbs. This stuff has been hashed out before. Look at the winning teams.

go back and research the "Bowman boundary layer" articles, Chrysler even had tech. sheets on them .
IF I WAS HAVING AIR FLOW OVER THE VENT PROBLEMS, I`d figure some way to put a big low restriction air filter on it, I run a
14x 4 1/2 " k-n , over a 1200 cfm throttle body. Altho intake height has to be juggled to a great degree.