A LOT of variables, cannot simply build an air pan and expect great results. You will need more jetting for sure. If the scoop is sized properly for the application you will certainly see a gain. Those lexan boxes are NOT sized properly for much more than a grocery store 318.

I agree with the many variables aspect, and why the results many report may be no more than GIGO.

I found this interesting, seems you don't have to build the scoop as big as you think you might.

https://www.dragzine.com/tech-stori...p-speed-with-a-forward-facing-air-inlet/

The air pan/ seal the hood works, BUT your scoop is too low to the hood ( air boundry layer) and too big of an opening, sealing it will catch a LOT of air at speed.
It sill take some trial and error, the solution for you may be seal the scoop and then block off the bottom part of the scoop opening. The "good air" is supposedly 2" above the hood surface. blocking some of the opening makes it smaller so helps with catching too much air at speed. Its some trial and error for sure.
In my experience though, cold air is always better and it will pick up something, how much ? go back to the trial and error comment

In your case as with ANY of the lexan boxes on a 2x4 deal it is NOT the right way. There is a pressure loss in the scoop as air passes the first carb. Keeping the scoop the same size front to rear ensures the rear carb will NOT see the proper amount of air/benefit. There is a reason scoops are tapered in the back, it is an attempt to equalize that pressure difference from to rear. althogh it will NEVER be the same. It is also an issue in a single 4 lexan box but the drop will not be as large since you are not pulling as much air at the front, but there is still a pressure loss to the rear.

In the OP's case he will likely need to make the air pan MUCH smaller than the scoop he has. But in the end to see any benefit is going to require some trial and error. As that scoop opening is WAY to big. But I think with some trial and error he will find a gain it will just take some work to get there.

How the scoop is configured inside matters too.

We fabbed a pan that went into the scoop - basically a Pro Stock style snorkel - to reduce the size of the opening and direct the air rather than just have it rolling around in there. Then used a pan on the carb to seal to that.

Not wishing to start an argument but you are going to have to school me on this, I have a question or two. I'm no expert by any means. My understanding is that in the example described in the article, maximum engine airflow demand (1600cfm) was achieved at 47.7 mph given the size of the forward facing opening. At any speed above that, would there be a positive pressure at the rear of the scoop as the scoop is now capturing more air than the engine demands ? I agree that there must be a difference in pressure between the front and the rear on open dual carbs but my home made makralon scoop uses a common filter (and is tapered towards the rear) will this make a difference ? Also what would be the right or best way on a 2 x 4 deal ? TIA.

Interesting results from everyone. Good timing as I'm currently building a cowl plenum induction on mine.

I have tested using a complete air cleaner, then the base only and then no air cleaner with a hood with no scoop on my old 1963 Plymouth 415 HP M.W. stocker, it ran .03 faster with the base only
Try testing yours and let us know what it does
I'll bet it is worth 2 to 3 + MPH increase in the 1.4 mile

Also don't forget, the cooler fresh air will most likely require more jet.

Couple guys here who have 1968 Hemi a-body type scoops on their race cars have made some air relief cuts or holes drilled in the back side. Maybe too much air coming in at speed messes up the carburetor signal?

My brother put an air pan on one of his cars years ago as it was burbling and not running totally smooth at the top end. It went slightly faster afterwards, but that may have been due to it being able to run clean all the way thru the quarter vs the pan being a speed adder all by itself.

A friend had a '65 Satellite with a sealed Hemi style scoop, no air filter and a flat air pan over a 360. Car ran well but occasionally slowed up on a run, then went back to what was expected. He cut a few "vents" in the sealing foam and the car stopped the random slower runs. We figured it had something to do with turbulence. I'm sure a good filter assembly or at least a good baseplate helps minimize any possible turbulence.

There's likely some good testing that was done back in the day as to the best execution on your car and scoop in the old DC chassis book. I know there's general hoodscoop practices chronicled which include scoop placement and inner scoop ideals. It's worth something for sure when it's done right. Outside air versus a mixture of radiator and header air is one. Not having air running over the carb and affecting the booster signals is another.

I riveted the pan to a drop filter base. That enables an inlet radius, the ability to use the original filter assembly and lowers the entire assembly.

At the time I was going 11.00s with a steal head 446ci motor.got a stop sign and made a air box to seal up against my six pack hood .on a November day got me a 10.85 123 mph