While we're talking about hood scoops............

IMHO, I think the hole should be as big as possible with the transition ( 90 degree air turn )as gradual as possible ( a big bell ). Also, as much space as possible between the carb air horn and the top of the scoop. I would think this would afford the least amount of turbulance.

I think if the hole in the hood does not match the base of the scoop you are not getting the full potentional of the scoop. But before you cut a bigger hole wait to see what some of the others like Mr_P_Body have to say. I have found that it takes more than you would think. Also I would think with the hole in the hood being smaller it would cause a turbulence more than forcing or having a fresh air effect for the carb. to pull air. On my R/T it work best with the hole & air pan cut to match the scoop. It worked so much better that on my dragster I built a pan not only to raise the scoop but to have more volume.

Bill my opinion is it will make a difference in the
height (where the carb is in relation to the hole...
is the carb still below the hole or is the carb in the
hole).... if the carb is below the hole and you can
mount a stub stack( my terminology I call it a "ideal
entry") so if you can put a ideal entry on the carb
and have the lip of it at the hole then the hole would
end up being the same size as the outer lip (just
smaller so you can seal it but not too small to effect
flow... if the carb is up into the scoop you need
to make it as big as necessary to get as much carb
up in there.... I think this is where the guys are
running into problems... not enough area above the
carb to get the air to make a smooth turn into the
carb... thats why I'm a firm believer in the ideal
entry to help (and you still need enough area above
the ideal entry... in this case(SCOOPS)... more is
better)...... IMO


Here some info from BG

There is no substitute for a well-designed fuel and air delivery system. By ignoring these two critical areas, all the work of building a strong powerplant is wasted.

Air Delivery
For maximum horsepower, the coolest, most dense air possible should be available at the carburetor inlet. Keeping restriction in the inlet path to a minimum - or better yet, pressurizing the air - is also desirable.
The denser the air, the more you can get into the cylinders. This allows the engine to burn more fuel and make more power. We recommend that a hood scoop or outside air intake should be installed wherever rules allow. Under hood air is heated by the engine and headers and reduces the amount of power that can be produced. A reduction in temperature of 10 degrees F. is approximately equal to a one percent power gain.
There should be a minimum of three inches of clearance between the top of the venturis and a hood scoop. If an air cleaner is installed, the tallest possible element is preferred with four-inch element preferred for racing engines over 500 HP.
When a hood scoop or external air intake is used, it is highly suggested that the carburetor be sealed to it. Otherwise, air will flow across the top of the carb and out of the inlet tract rather than into the air horn. If air is forced past the carburetor it can siphon fuel, causing the engine to run lean. Windshield snorkels are especially notorious for siphoning unless the rear is sealed. Air pan kits for sealing the carburetor to the scoop are available or they can be fabricated. An air bell or radiused intake should be used whenever possible to increase air flow into the carburetor.
It is not unusual for a drag race car to improve ETs by 0.3 second and increase top speed by as much as seven miles an hou after installation of a sealed scoop. A car will not pick up ET after the scoop is sealed off if the scoop is too short or the fuel delivery system is inadequate.
On oval track cars, the same is true. Paying attention to the inle tract design will pay off. Depending upon track length, oval track cars will typically improve lap times by 0.1 to 0.5 second once an optimized air intake system is installed.

I have a 6 pack style hood on my car & I dont or haven't yet tried to seal it up. However I have tried 4 different air cleaner assemblys & lost over a tenth when I went from a 14 inch round 2 inch high to a small thin style with an open top. So to add to what Bill is asking. Could it be that the larger air cleaner helped fill the hole & reduce turbulence or is something else going on.

The carb is currently still below the hood line and not up in the scoop.

That may change though. When we dynoed the first build we did we found the the 2" APD black widow spacer made significant gains in HP and torque.

Unfortunately, we never got the chance to try an on track test to see if those gains carried to real world ET's

My point is that the addition of that spacer might move the carb up into the hole or at least maybe have the top of the carb flush with the bottom of the hood.

Curently, the carb is about 2" below the bottom of the hood. Which puts it about 7-9" (roughly) below the bottom of the opening in the scoop.

Yes the scoop is molded onto the hood. (I can only hope it never becomes separated )


So, if I don;t have the spacer putting the carb flush with the bottom of the hood, then the next ideal entry would be something like



With the top sealed to the bottom of the hood and the hole in the hood matching the top of the sack?

Raff asked me to post this.

and this...

I think I get it.

Not sure if I can pull it off but I think I get it.

bill i have a filter base i am not using that you could use if you like.i will measure the rise and take a pic for you sometime this weekend.

Nice smooth entry, with at least 5" from the top of the scoop to the venturi's. I run a 4" scoop, so from the hood line to the top of the scoop in the pic is 4". I am not an expert on air flow, but I have a brother who ran the air flow room for I.H. for over 25 years. Even designed his own air flow bench and flowed turbo housings on the side at home for a little extra $. Yes, I can get all my stuff flowed for free. All I have to do is make the adaptor. Aint I lucky

Crizila pan looks like it will work,should have enought volume. Then I am not and expert on air flow either But I have found on mine & a few others you can have to small or not big enought of a entry & it will hurt the HP,have yet to see one that was so big it hurt the HP.

Mr_P, Would it not be better to have the hole somewhat the shape of the scoop,than say a somewhat square scoop with a round hole? That's only a question,not saying its better. Just trying to learn all I can.

PS I even painted the inside of my scoop hoping it being smoother it would help the air.

i think we could take ideas from dragster scoop pans and ith some simple tool make something for Bills application.maybe even with it bolted to the carb and sealed up in the scoop.