Lower cowl under fan is open to the road?

[BadDog]

I thought I knew square bodies fairly well, but keep finding new stuff I didn't know (or forgot?). The latest was found while fooling with reworking/resealing the air box, which was stripped to the fire wall. I was amazed at the amount of dust and debris in there, but I've seen and cleaned that before. What I don't recall noticing before is that the lower end of that air return cowl pocket is has an opening about 1" x 3" at the bottom.

I first thought maybe there was a missing plug or something on my Sub, so checked my donor K5 and it has the same opening.

I assume it's intended to introduce some outside air. But that makes little sense given that it's going to be sucking in dusty debris thrown by the passenger front tire.

Searching this site and others has been fruitless, probably because I don't know what to call it. So, now I'm not sure what (if anything?) to do about it. Does anyone have any information on this? Or what method of blocking it up would be a advisable, or perhaps inadvisable?

I certainly don't want to be sucking dust into my nice clean ducting system, and in Phoenix I would prefer to avoid pulling in hot air right off the pavement with 110*+ ambient...

 

[6872xtc]

If I understand your description correctly, you are asking about the hole that is at the bottom of the plenum where the kick panel vents get air from the cowl, correct?
The top is open to the cowl, and the bottom is designed to let junk and water drain out. But leaves and pine needles do a nice job of plugging them up.
I do wonder if it is s relief for any excess air getting pushed into the cowl while driving down the road.
I do know from running around with the vents open in the kick panel, there is a decent amount of air coming through them, which I don't see any way that is is coming from below if the air pressure is higher at the cowl.

But if it gets built up too much, plugs the hole and packs down, you can end up with water inside. It will come through the kick panel vents.

 

[BadDog]

Yeah, that's the one.

I was wondering about that. I always understood the "outside air" source was the upper cowl, and obviously it clearly needs to drain, but the amount of dust and debris I found in the ducts was pretty bad, so I was assuming it was coming in from that big open hole right behind the front tire. It just seemed to me there should be something down there to keep it from sucking in dust and hot air, but maybe the cowl pressure area makes sure the flow goes the correct way. What about when not moving forward at sufficient speed?

I also found dust tracks through 2 areas where the box is supposed to seal to the firewall. Those 2 areas just didn't seal, looks like missing/thin seal material, and I'm assuming OEM. But that area is supposed to be pressurized by the fan, so assuming it was pushed out of the dusty vents. Then again, with fan off, maybe it can become negative. Not smart enough to figure out those fluid dynamics. I wish I had taken pics or paid more attention to the dust tracks, but it's all cleaned off now ready to reinstall. Mainly I just want to figure out and address the source for all the dust I found in the ducts...

 

[6872xtc]

I believe that the theory was that the front fender curved under enough to block stuff getting thrown up into the bottom. Just my opinion.

And as far as air coming on there at very low vehicle speeds, I would guess that is possible, I don't have any hard evidence.

And as far as keeping it all clean inside there, I would think that you would have to add some filter media up top and at the bottom, but cleaning or replacing the bottom one would be difficult as crap!
Make sure that you use something that doesn't come apart during a rainstorm or wash job.

Now you have me thinking about adding a filter to mine...

 

[BadDog]

LOL. I often think myself into something of an analysis paralysis on stuff like this.

In any case, it seems it would almost have to be some sort of modular soap bar shaped filter that could slide up from the bottom and lock into place. Then cleaning is easy. Not sure what to do on the top, no easy access.

But, my main point in posting here is satisfied. I just wanted to make sure there wasn't something like the floor drain plug things that was intended to at least provide some blockage down there while still allowing drainage and cleaning. Like the starter and trans braces that are too often left off and lost along the way..

 

[6872xtc]

The cowl panel isn't terrible to pull if you are only doing it once a year or so...

But you may be in a world of trouble relying on my memory!


Ask @azblazer or @Bent77 ...
Well better not...

 

[BadDog]

Can't be worse than relying on mine. I've forgotten and had to relearn a lot of stuff I KNOW I used to know, but now the only thing I know is that I don't remember. Eh, what was my point...?

 

[imiceman44]

Can't be worse than relying on mine. I've forgotten and had to relearn a lot of stuff I KNOW I used to know, but now the only thing I know is that I don't remember. Eh, what was my point...?

I hear you.
I forgot more than most people know.

 

[Moody Bricker]

I thought that is where the dam mice come in,so I was going to put in a screen.