Carb Air Box
 

At the track last weekend, I met another racer with a Barracuda who also built his own air tray. We talked, and I commented on the fact that my box (sealed to a Harwood Aero scoop) catches so much air that the rear of the hood lifts some. He told me that he had the same situation once, but a friend of his recommended that he open a slot at the rear of the tray 2"x3" to let some air flow out and he picked up 3/10ths. Should I believe him? Any thoughts or experience with this?

Picking up 3/10s by letting some air out of the box sounds like an awfull lot.

I can see picking up that much by going from an unsealed carb to a sealed carb, though.

I used to have a cheesy fiberglass hood with a giant scoop on it:

http://www.elite-computing.net/racin...s/10790595.jpg

This hood would rise up so much in the back that at the top end of the track I was able to see the carb. When I put one of those Moroso air pans on, which sealed the carb to the hood, that problem stopped.

Does this help any?

Wow, never saw a scoop quite like that....wonder how well it worked. The ramp out front is an interesting design.

Well, I decided I'm going to try out what the guy told me and see for myself if it does what he claimed it would do (nothing ventured=nothing gained). I'll post the results.

Haven't been able to find much information on the net about scoop designs and favorable air flow characteristics; all I did find was that what is desired is high volume and low pressure but no information on how to achieve it. Perhaps by providing a pressure relief point at the rear of the tray, you effectively lower the pressure of the incoming air without lowering the volume (just thinking out loud).

From what I found on the 'net, that was a "70's Pro-Stock style" scoop.

It was too damn big, I couldn't see over it half the time. I went with a six-pack scoop on a different hood. Much better.

Exactly, you never know until you try!

that was a hell of a scoop. :shock:

Air Pan
 

Have a snorkel scoop on my chevelle. Made and air pan for it and it picked up a tenth.

Started having some problems down track on the gear change. Of the many things that were looked at the scoop and air pan got some attention. One of my friends spent some time on a pro-mod team which had some scoop related problems.

If there is no relief for air pressure building up at the back of the scoop it can actually form a dam. The dam can back up and block air flow down into the carburetor.

You do not want the area inside the scoop to be any larger than necessary. Scoops are big in the outside but a lot of testing and work is done to the inside on fast cars.

Making an opening in the back will relieve pressure. A spring loaded trap door will regulate the pressure and open when necessary.

By the way the problem was the converter. In the process some other problems were found and fixed. Several things overlooked previously were improved.

Welcome Signman. Thanks for the good info.

The idea of a spring loaded trap door makes sense to me; this way you are not sucking in any hot air from the engine at idle and at WOT the scoop will relieve itself from too much air pressure causing that "dam" effect. Now I have to go engineer one.

one thing you can depend on its always something in our persuit of speed and thee better et. welcome signman.

Well, I did cut out a 2"x3" opening at the rear of the air box, and made 7 passes on Saturday. The air was bad that day and I still managed to run my normal ET, so I guess that's a positive outcome. Another trip or 2 will be more telling.

Was the hood still lifting or did this correct it?

Im about to make a pan for my scoop. Found the perfect peice of aluminum for it. Already cut to the right size. I just hope all the air being trapped in their doesnt rip the hood of the car :?

what do you mean a pan? to fit around your air cleaner?

It sits under the aircleaner (actually attached to the base) and will have foam around it to seal to the under side of the hood.

gotcha

Mikels old scoop was a 70's Mopar pro stock scoop. That was "The" scoop to run back in the day. That spring loaded door for the pan is a great idea.

Well, I finally got around to making the spring loaded trap door for the airbox. The toughest part was finding a spring with just the right amount of tension, which I never did find. Wound up using a single strand of rubber band. Tested it out with an air gun using low PSI; it opens and closes. It's ALIVE...It's ALIVE!!! (mad scientist laughter ensues) :badgrin:

Pictures?

Posted a couple of pics of the trap door on the air pan (sorry, I'll try to get a better quality pic). Used a single strand of rubber band for tension which seems to work well, however, durability is in question. Need to find the perfect spring to replace the band. It works well, the hood doesn't lift up in the rear anymore. :mrgreen:

Is that a kit sold some were? Or did you fab it.

I made the whole thing. Yessirr, guilty.