Did a better job of taking pictures for this little project, so here it is:
Tbear853 cowl vent covers. was the inspiration, but also something I’d been considering for the sake of pine needles and leaves building up in the cowl vent wells. (Im also hoping it’ll help stop a persistent water leak from the firewall area)

It took me about 4 hours start to finish, with all the right tools and materials on hand; your mileage will vary depending on skill level and what you have available.

Materials:

-at least 8”x24” .110” acrylic sheet (I wouldn’t use anything thinner in acrylic, and lexan would be better)

-8 or more 1” long 10-24 poly (plastic) machine screws

-11/32” wide strips of 1/4” thick poly sheet, 8”-10” long total (for T-nuts, or just buy 10-24 T-nuts that are a little under 3/8” wide to fit through the grill)

-10’ of 1/4” (or so) rubber line/tubing if you want a gasket around the outside to protect paint

Tools:
-Sharpie
-24” long straight edge
-12” tri-square
-angle finder or protractor
-measuring tape
-cordless drill
-grinder with thin cut off wheel
-clamps
-table
-10-24 tap or 10-24 metal machine screw
-Uni bit or 1/4”(ish) twist bit

PPE:
-safety glasses
-respirator or dust mask
-ear muffs or ear plugs
-work gloves

-Start by cutting your two sides out of your cover material. Clamp your material to the table, mark, and cut with your the grinder. Cut two pieces 4” wide, and at least 24” long, preferably a little longer if you can. Dont forget your PPE; cutting acrylic with a cut off wheel makes quite a mess, and try not to think about microplastics.

Props to Tbear853 for this as a starting point. I’d suggest use this for the Driver side start, then wait and adjust your passenger side for the wiper cut out. See below.

-Next mark one piece up as seen below, ensuring you have at least one straight clean edge to measure from. Note the angles on the ends, which end is which, and which side you’re measuring from. (You can measure from the bottom/front, just reverse the angles; ie 95* bottom right corner, and 85* bottom left corner.) (Don't start cutting until everything is marked, it’ll make it easier.)

A bit of a mess, but easier to show with pictures.



-Now mark up the passenger side as below.

-It’s not shown entirely, but the below picture already had the back/top cuts made, but is shown in writing in the piece.


-Cut your pieces out with the grinder carefully, using the table annd clamps, and lay them on your cowl and mark to clean up edges. Also lay out your attachment locations. I put mine in the middle of vents, with one on each end, and one other in each section. (I also only had 8 screws on hand)

-Drill carefully into the acrylic, preferably in reverse with high speed to “burn” through so it doesn’t crack.

-And finally note the T-nut set up written in the picture below. If you need a gasket, use 1/4” or so line/tubing, cut down one side, to snap over the edge.


Sorry I had to rush at the end, and hopefully didn’t forget too much; family just got home and I’m outa time. If you’ve got questions, reply or PM me, and I’ll try to address them if you need.

 

Bonus install tip:
Run the machine screws most of the way into the T-nuts, put the covers in place, then back the screw out while pushing down on the screwdriver slightly, until the T nut clears the grill and starts to turn underneath. Turn til it lines up how you like, then release pressure from the screwdriver. The T nut should stay in place while you gently adjust/align the covers, then gently snug them down.

 

Bonus round:
What semi-useful system will be rendered useless by this mod?
………
………
………
Times up; pencils down.
No Timmy, the answer is not emissions.

The correct answer is windshield washers.


Fixed with a 1/2” countersink run in reverse after lining up, leading, and marking where the sprayers are at. Only had to chamfer the drivers side a little to get it to clear the stream.

 

I don't understande why you would do this. If your drains are clear you shouldn't have leakage, unless you have a problem elsewhere. You just blocked off the air to the heater and AC.

 

Thanks for the feedback.

Pine trees for one, of which I have several adjacent to where I park. Also trying to reduce possible leak areas, or verify where they aren’t. I also have the Hi-Lo system, so as far as I can tell, most of my air settings are re-circ anyway, and if they weren’t before, they are now.

Also same guiding principal I had with burning a bunch of time and a bunch of money on an almost 50 year old truck (or motorcycles, or house)…. Seemed like a good idea at the time, lol.

 

Why not use screens rather than plexiglass?

 

While I had mine in place (before all the body work, paint, tree removal,etc) keeping pine needles & leaves out, etc, I did drive the truck a time or two. Heat, vent with the AC still moved air, just not as much. My guess is it was still drawing a vacuum in the cowl bowls and pulling some air through the cowl drains? Screens would work, some have installed such. Tape, or even cloth would work to various degrees. I recall one poster (forget who on what forum) cut his out and welded in solid sheet and painted, it.

Was a time I had a old folded car cover pulled over the back of the hood, the cowl, and the windshield and wipers, and a piece of rope tied from mirror to mirror to fight the wind. I never drove it with that in place, but it made snow removal easy.