47-55.1 Cowl Vent Vent

[Father&son56project]

Yes, you read that right! On my list of things to do this winter on Project Fargolet is an improvement to the cowl vent system. The truck does not have A/C or any other vents, so that cowl vent is a godsend on hot days. Even on the worst days, it keeps my wife and I comfortably cool. We are in a rural area, so there really is no such thing as “being stuck in traffic” so continuing on without A/C is fine by me.

There is however one drawback, and that is noise. All that air that comes shooting in through that vent has gotta go somewhere, and that somewhere is either door or window seals as everything else is perfectly sealed off. There is a big difference in interior noise once that vent opens, and of course the whistle and racket of the escaping air is right beside us. I was thinking about fabbing up some sort of hinged flap under the seat that I could open up when I want cool air and some peace & quiet. My exhaust exits at the far rear of the truck, and the rest of the exhaust system is new & leak free, so I am not too worried about that. It’s also a “sunny day” vehicle, so I am not worried about water spray under the cab. So my questions are:

-Has anybody done something like this?
-Is there some basic thing that I have not thought about (I don’t wan’t to fab something that is stupid or dangerous (or both!)

Any thoughts out there?

[dsraven]

I plan to use the cabin venting system from a donor vehicle. on newer vehicles there is a plsatic frame with little rubber flaps that normally sit against the plastic and seal the cab from outside air etc. when you open a vent to the outside or close a door so cabin pressure increases these little flaps open and let the inside pressure out. if you look at the door of a lot of vehicles you may see the plastic thing. newer vehicles may have them in the rear wall of the cab where nobody sees them unless the box is removed. some vehicles hide them behind a plastic bumper and these tend to be larger. my 2015 silverado has them in the back wall of the cab with a plastic and/or rubber stip between them and anybody who may be looking from the side so they are kinda hidden plus the plastic/rubber strip keeps the car wash pressure from getting blown into the vents and onto the floor of the truck under the back seat.

pretty cheap too, all things considered, but they gotta be mounted right side up to keep the flaps closed. if you have interior panelling just ensure there is some way for airflow to reach the vent outlet. here is a link to the 2015 vents. rectangular so easier to cut in and retain.

https://www.tubmangmpartsdepot.ca/p/...caAlPUEALw_wcB

and of course the Canadian price.....

https://www.amazon.ca/Genuine-GM-Val.../dp/B00TABJ09W

or the wreckers have them, just gotta find a good one and clean it up.

[dsraven]

my 2015 has a couple of these. it allows you to drive with the windows closed, less bugs on your arm sleeve. haha

[leegreen]

I would be hesitant to take air from under the cab, it could easily get exhaust or engine fumes. I know your exhaust is on the other side, but there is a lot of turbulence under and behind vehicles so the air mixes in strange ways.

Maybe try driving with the factory battery box lid or the master cylinder access plug out as a test - if you have those still.

dsraven, I wish I had read your post before the box was on, adding a rubber flap vent makes a lot of sense

[dsraven]

good point LG, the air under the cab can be dangerous, and also hot anyway. better to draw it from behind the cab or a door jamb prolly. behind the cab is likely a low pressure area swirling around so air would flow through the cab well. just install the vents higher than at floor level.
if you wanted to get fancy pants and have the vent above the box rail level there are some chrome vents that are used in the marine sector for venting engine bays etc. one could look at something like that. older boats may have chrome ones, if you like the look of chrome.

[Father&son56project]

You learn something everyday! I was unaware of those factory flap vent things, but something like that could be just what I need (and it saves me having to fab stuff up). As for air under the cab being hot and potentially having some fumes in it, remember that what I am after is an air exit, not an intake. The cowl vent on the Fargolet scoops an obscene amount of fresh, cool air into the cab, but that air needs an escape. I can roll down a window a bit, but the resulting noise is pretty bad. For me, the most convenient place would be under the seat as it is far from my ears, I would not have to cut a hole into the rear of the cab, and I would not have to remove and modify the interior panel. Air does however do funny things, so the suggestion about running a test with the battery cover removed is a smart idea. Of course I did a wonderful job of sealing it, and then covering it in sound deadener as I knew with absolute certainty that I would never have to use it!!!!

Thanks guys!

[leegreen]

I misread your post as wanting to get air into the cab from a quieter source.

for a more in keeping with your build approach, you might look at early-mid 60s pickup kick panel vents. both ford and GM had them on removable flanges. Steel flap doors, I think Fords had a thumb screw, GM had a spring latch
Vans had such vents well into the 70s, but not as a removable unit.
I'd probably add some mesh to keep out critters when I forgot to close it

I checked your build thread, very nice truck!

[mick53]

Is behind the cab a low pressure area? Would you get flow? Maybe I'm reading this wrong.

[dsraven]

when you get it figured out after a test run you could try using a plastic knife gate or slide gate valve for plumbing. it is used in stuff like hot tubs and spas and such. you could install it wherever and have a cable to operate it. like if it was under the seat, say, you wouldn't have to move the seat to open or close it.
if you want it under the seat that is. they seal the weather out and don't take much space. I will punch a hole in the back wall of my truck because I want it to have flow all by itself as well as the ability to equalize pressure while closing a door etc. to each their own.

[dsraven]

Mick, I assume it is by the way the snow swirls and drops out on my tonneau cover right behind the cab. With a higher cab pressure it may flow well.
Just spit ballin.

[Father&son56project]

Leegreen, you didn’t misread it, I just worded it poorly! Both your idea (kick panel vents) and dsraven’s ideas (gm air pressure relief vents or a simple gate valve) will save me from having to create something from scratch. Funny thing, as I was getting ready to dispose of all the leftover junk from my build, I looked at the rear of my S10 cab and saw a little plastic grill. At the time I wondered “what on earth could that thing be?”. I’m willing to bet that my Blazer parts truck (that I also recently discarded) also had one. Nuts!

This forum is incredible. Those simple solutions would have never occurred to me. Thanks guys!

[mick53]

In the mid eighties I lived in the SoCal desert. My 53 was my construction work truck. I used to put a cooler under the cowl vent and fill it with ice for A/C. 1 bag would get you home.

[joedoh]

on my 65 i always planned to have a new back glass made with holes in it for pop out hinges like on s10 ext cabs. there is a local shop that as long as you give them the template they will cut it and temper it (gotta cut and drill before tempering, cant drill tempered glass). so i planned to make a masonite window and drill holes till i could get it latching and hinging correctly on the outside of the window gasket and then have it made and install it. a small window like in these cabs would be even easier, i think someone in the projects has actually done this. i dont know how it would work on your fargo though haha

[leegreen]

tempest67: "I thought it was going to be great, However, I am disappointed as I find that it draws in warm air and lots of noise."
post #10 here https://67-72chevytrucks.com/vboard/...d.php?t=827764

when I was a kid our '67 dodge camper van had pop out rear windows, they sucked in exhaust at any speed

[dsraven]

I suppose you could tie or tape some ribbon to the sheet metal or window of the area where you may wanna install a vent, then drive the truck and see what the ribbons do. kind like a cheap mans wind tunnel.
good point on the noise thing though and possibly the exhaust fumes, depending on the aerodynamics of your truck. I think, with the little flap door things, they are usually behind some sort of upholstery. not too many newer vehicles have a bare cab wall. that may make a difference for sound. the upholstery would need to be vented to the cab area from the backside though, for access to the flap door things.