Wiper Cowl

[greasemonkey]

My artistic side flaired up, couldn't help myself lol
The cowl provides air to the kick panel vents and the blower motor.

[Harold Shepard]

There is a divertor located on the inside of the cowl, part of the air flows to thr air vents on the kick panels , but air is also diverted into the squirrel cage by divertors welded into the plenum on the passenger side. How do I know you ask, because I have had the pleasure of rebuilding my trucks inner cowl area from the inside out for the last three months, all I can say is glad this project was free or it would have been a beer can by now.

[Classic Heartbeat]

The heater on draws its air from the cowl. Here are the pictures to show you why. The round hole is where the fan is. With the seal in place you can see that it can only get air from that hole. That hole is in the firewall cowl area, where it draws air from the holes in top of the firewall, under the cowl. WES www.ClassicHeartbeat.com

[68LSS1]

Thanks guys. That makes sense. So I think that one would be able to weld up the cowl and make a few small holes which could be made larger later if necessary. If it is welded up without adding these holes airflow would suffer big time. I would locate the holes in the "boxed" section facing outboard on both sides. I don't see why that wouldn't work. Anyone?

[purple gas]

the heater and vents get air from the cowel vent. If it got air from inside the truck, it would be re-cycling air in the cab. Sure it would warm up faster, but it would also re-cycle the humidity and make it impossible to de fog your windows. Air comes down the side of the cowel inside your right fender, and into the sealed box, through the heater core, then is distributed to either your floor or windsheild vents. the box is sealed partly to keep engine fumes out of the cab. The cowel vent area ( where the plane of the hood intersects with the plane of the windsheild) is a natural high preasure area created by turbulance when you drive down the road. drawing in fresh air . If you have an inlet getting air from lower down you could possibly get any fumes that might be produced by the engine.

[FRENCHBLUE72]

That cowl area is not the only place that air enter's the cab area,if it was your truck would explode at the seam's from the force of air if it had no where to go (like when the vent's are closed)...Even if you shave the cowl vent's you are still gonna get air from somewhere the cowl area is not gonna run out of air...Btw if the blower motor is sealed to the firewall how is it gonna use recycled from inside the cab???

[SCOTI]

Originally Posted by purple gas

the heater and vents get air from the cowel vent. If it got air from inside the truck, it would be re-cycling air in the cab. Sure it would warm up faster, but it would also re-cycle the humidity and make it impossible to de fog your windows. Air comes down the side of the cowel inside your right fender, and into the sealed box, through the heater core, then is distributed to either your floor or windsheild vents. the box is sealed partly to keep engine fumes out of the cab. The cowel vent area ( where the plane of the hood intersects with the plane of the windsheild) is a natural high preasure area created by turbulance when you drive down the road. drawing in fresh air . If you have an inlet getting air from lower down you could possibly get any fumes that might be produced by the engine.

Sounds good, but isn't logical. I don't remember humidity decreasing w/speed.
If the air being recycled in the cab is humid and "makes it impossible to defog your windows", it is humid for a reason . . ....the humidity outside the vehicle. When the vehicle draws in all that "....high pressure..... fresh air....." it will contain as much humidity.

The cowl vent is a sealed fresh air inlet for the cab that doesn't require opening a window to get. I'm not being sarcastic or trying to cause trouble, just offering a different perspective.

[Classic Heartbeat]

The cowl is there for a reason. If you seal it off, sure you will get air from somewhere, but the question is where? Will it recirculate from the inside of the cab causing it to implode...lol (poor attempt at humor) It will recirculate air some from in the cab, but not enough to cause implosion. (although that would be cool to watch.) Odds are though it will pull more air from the engine compartment through the drain holes. ( air barely fit for the engine, let alone someone driving the truck.) I'll keep the cowl vented, and just add one of our screens to keep the debree out... WES www.ClassicHeartbeat.com

[purple gas]

When I worked at a car rental company in winter we'd get calls from people that the windows would fog up. ( most newer cars have a re-cycling button in the dash). Invariabley the people would have the button pushed in. Sure, the car warms up faster, or cools down faster with the A/C on, but it's not getting fresh air. Humidity can come from breathing (ever make out in a car?), or melting snow from yer boots. If you don't displace this humid air with new fresh dryer air, it condenses on the windows if there cold. It won't implode or explode, but if new air can't come in, the old air won't be displaced. look at the owners manual of most cars and there will be an ilustration of where air Exits the vehichle. If your building a show truck, or you live somewhere where you don't need heat,de-frost or A/C, fill the cowel in, you can always roll down a window or put on a sweater. But by the looks of the trucks in the posted picks, I doubt if those trailer queens ever see a rain drop, much less an icy road

[68w/sbc406]

ever notice how your windows defrost faster when the AC is on? and new cars the AC automaticly comes on when you turn your defroster on? i dont think it is just fresh air that stops the foging. my windows barely defrost when the heat isnt on but the fan is full blast. plenty of cold fresh air coming in.

[purple gas]

this could go on forever...But.. Your windows defog faster with heat, becasue it warms up the glass. moisture condenses on colder things faster. Breath on a window in summer, you may see a little fog,, do it in winter and you get lots of fog. (unless you have tripple pane windows with argon between the panes) ............Basically my point is this. for the heating system in a truck to work you need an adequite supply of clean fresh air. Air from the cowel is clean beacuse it's not contaminated by fumes from the motor, and plentiful because of high presure created by aerodynamic forces when you drive down the road. Thats why they put the cowel vent where they did, and still do in cars built today, that's why cowel induction hoods have the "scoop" facing the windsheild, it's a high preasure spot and air is "forced" into the opening. If you need heat/defrost/A/C, you need air flow. Sealing the cowel vent without providing an alternate supply of clean fresh air is similar to having a plugged filter in your furnace, or your wifes hairdryer inlet full of lint..... If air can't get in, the fan can't blow it.

[68LSS1]

I will be using a aftermarket heat and a/c unit with the cowl closed up. With the installation of this unit the air will be drawn in from the cab. I'm sure the heat and a/c will work just fine. And as far as the blower motor I meant sealed as in not having any air inlet in the engine compartment. I forgot the motor wasn't actually in the box but had its own hole. Tend to forget stuff when it's long gone and your firewall is smooth and clean. It's a good thing it's impossible for the blower motor to create and pressurize a cab. There would be cabs coming apart everywhere, lol. I agree with 68/wsbc406 above. A lot of newer vehicles do not have a fresh air option, especially trucks/suvs. You crack a window or run the "climate control" system.

[68LSS1]

I disagree purple gas. When I get in my car at 0200 every morning I use the a/c for defog. It works 10 times better than heat.

[purple gas]

OK,, then lets settle this like men,, I suggest pistols at dawn, 20 paces, turn & fire. Just kidding. If I can figure out my scanner, I'll send you some Quotes from the owners manual from my 2004 chevy van. It says "Fog is casued by moisture condensing on cold glass". The A/C may work becasue when the air is cooled, the moisture is taken out of it. (Thats why air conditioners always have a place where water drains away. Cold air can't carry as much moisture as warm. That's why when it's 40 below where I live the air is very very dry, some people have to use Humidifiers in there homes or they get nose bleeds in winter) Perhaps the air from your A/C is dry enough to dry the fog off the windows. May be a geographical consideration here. The climate in Florida is much differnt from here in Saskatchewan where I live. I don't imagine you need a Humidifier in your house.

[SCOTI]

Originally Posted by purple gas

OK,, then lets settle this like men,, I suggest pistols at dawn, 20 paces, turn & fire. Just kidding. If I can figure out my scanner, I'll send you some Quotes from the owners manual from my 2004 chevy van. It says "Fog is casued by moisture condensing on cold glass". The A/C may work becasue when the air is cooled, the moisture is taken out of it. (Thats why air conditioners always have a place where water drains away. Cold air can't carry as much moisture as warm. That's why when it's 40 below where I live the air is very very dry, some people have to use Humidifiers in there homes or they get nose bleeds in winter) Perhaps the air from your A/C is dry enough to dry the fog off the windows. May be a geographical consideration here. The climate in Florida is much differnt from here in Saskatchewan where I live. I don't imagine you need a Humidifier in your house.

The a/c works to eliminate fogging because the system incorporates a drier to eliminate moisture/humidity, not from outside 'fresh' air.

[purple gas]

I'll buy that explanation Scoti. I guess it depends where you live. My part of the planet windows fog, or frost up becasue there cold. Any day now I'll have to let my van run for 20-30 minutes in the morning to warm it up enough so I can drive it and still see where I'm going. That's if I rememberd to plug it in at night and the damn thing will even start. Living in these conditions, heaters/defogers deal with conditions you sunbelt boys don't have to worry about. I'll keep that in mind next time I offer advice.

[GMC AMI]

Has any one seen a chrome one installed?

[SCOTI]

Originally Posted by purple gas

I'll buy that explanation Scoti. I guess it depends where you live. My part of the planet windows fog, or frost up becasue there cold. Any day now I'll have to let my van run for 20-30 minutes in the morning to warm it up enough so I can drive it and still see where I'm going. That's if I rememberd to plug it in at night and the damn thing will even start. Living in these conditions, heaters/defogers deal with conditions you sunbelt boys don't have to worry about. I'll keep that in mind next time I offer advice.

As will I. The biggest thing in DFW is humidity. The drier in the a/c system will work faster than a heater to defrost windows around here. Since I don't have working a/c, and still have a cowl vent on my 74, I rely on some temp, a med fan speed, & the a/c ducting diverted to defrost to clean my windshield @ 5am.

[purple gas]

One thing I know no matter where you live. If you keep the glass clean on the inside they are less likey to fog up. That has little to do with closing off cowels but this poor thread has been off the rails for quite some time now.