Inner Cowl Drain Holes

[COOP3726]

O.K. guys. I purchased a 1972 and I noticed the cowl has some rust above the blower motor. I have been looking at all of the write up on the inner cowls and I have not seen anyone of them that has a solution for the issue these trucks have with the drain hole being to small. My question is, why can't these drain holes be opened up to let larger debris pass through? Has anyone attempted doing this and does it work?
Thanks.

[Andyking1203]

I think if you open it up, you would have a problem behind the fender.. lmc has pieces that will "plug" the cowl pieces and stop crap from getting in there...

[Getter-Done]

Here is a thread that talks about some guards.

http://67-72chevytrucks.com/vboard/s...ht=cowl+guards

[COOP3726]

Thanks, AndyKing1203 and Getter-Done for the reply. I'm aware of the guards for the outer cowl, but this is not the answer I am looking for. My question was, Has anyone attempted making the holes larger and does it work?. There has to be another solution. What about pine trees. Pine needles will go through these holes on the guards and do the same as leaves. I'm not really sure what the fender looks like on the back side and how it effects the issue on these trucks.I guess I will find out when I start on it. I do know some of the issues that was on the 1985 Silverado's, because I have one that I have almost completed the restoration on and it had some issues with rust as these trucks have. This '72 is my next project and I have been trying to get rust info before I attempt to tackle the restoration on it. When I start the restoration on this truck, hopefully after the holidays, I will start sending out pictures. I have attached a few pictures of the '72 Highlander & '85 Silverado. Thanks again for the replies.

[Andyking1203]

Nice square body!! Theres a typical GM truck problem with the 72s, that the back of the wheel well of the fender will rust and rot out eventually, when you take the truck apart you will see how the crap will fall straight through, this how it looks behind the fender

[COOP3726]

Thanks, I have been working on the Silverado for some time now and almost completed with it. I hope to be able to take apart the '72 soon. Once I get the finders off of the truck and look at it I will see if there is another way to make it work. If I do I will keep everyone updated on it. Thanks again for the reply and picture.

[B. W.]

Here's some pics of the drains. They are pretty large but you could make them bigger. The only issue I see with them being larger is on A/C rigs, when on recirculation it will allow more outside air into the system. Might not really matter.

[COOP3726]

Thanks for the pictures B.W. I don't know if that will make a difference or not, but it looks like they can be larger. The air motor will only pull so much air when it is working. I guess it depends on what the back side of the fender looks like, whether or not it can be done without causing any issues. Thanks again for the pictures.

[Getter-Done]

Nice work on the Square body.
Looking Good.
I will stay tuned too see your idea you use for the drain issue.
It could save me some modification time.
I did not realize you was doing a restoration in your first post.
Since you are I will share my thought on this.
I have my cab off the frame and it is just a bare cab currently.
I am going to bolt the fender on
and see if there is enough room to change the angle from what is now
(approximately) 10 degrees
and try to increase it to 15 to 25 degrees which will
let the leaves and stuff wash out easier.
Of coarse metal will have to be
added and removed and the fender tapering down will factor in.
It just something I am going to look into while I am in the build.

One of the best memories I have of these trucks is
getting in my Grandpa's 71 Chevy
and opening the side vent
so the leaves would go flying around in the cab
Grandpa always got a kick out of my Free entertainment.

[GMCPaul]

They made the cowl vent doors easily removable so that debris could easily be removed. If you open the drain further all the debris will now settle between the fender and cab resulting in faster rusting from the inside out in those areas. If you park outside expect to clean out the cowl vents multiple times a year, if parked mainly indoors once a year should suffice. If you open it up to let the debris out of cowl expect faster rusting of rear of fender, and forward side and underside front portion of the cab. So in my opinion you'll just be trading a area you can clean out to a area you can not clean out nearly as easily.
Just my opinion.
Paul Sr @ GMCPauls

[Getter-Done]

Originally Posted by GMCPaul

They made the cowl vent doors easily removable so that debris could easily be removed. If you open the drain further all the debris will now settle between the fender and cab resulting in faster rusting from the inside out in those areas. If you park outside expect to clean out the cowl vents multiple times a year, if parked mainly indoors once a year should suffice. If you open it up to let the debris out of cowl expect faster rusting of rear of fender, and forward side and underside front portion of the cab. So in my opinion you'll just be trading a area you can clean out to a area you can not clean out nearly as easily.
Just my opinion.
Paul Sr @ GMCPauls

Good point

[COOP3726]

Let me give you guys a little background on myself. I started restoring cars and trucks when I was 19 years old. My first restoration was a 1970 Nova. Sold it, bought a 1967 Chevelle, sold it, and bought a 1965 C10. I restored it and kept it for 18 years because of marriage and two boys. Decided to sell and buy a camaro, but could not find one to my liking. A friend of mine pointed me to a 1962 chevy II and after purchasing it I found out it was a rust bucket. That discouraged me somewhat, but I completed the restoration and it won a lot of car shows. I have always been mad at myself for selling my 1965 c10, so I decided to purchase another truck. I like the looks of the 1969-1972 c10. I think they are the best looking trucks chevrolet has made. But my wife wanted me to purchase a truck like her dad had before he died, so I found the 1985 Silverado which I am about finished with, which you can see in the pictures I have posted previously. Oh by the way; I do all of the restoration myself from welding to painting and complete frame up.
Now that I am 1 month away from 64 years old, I can start on my '72 truck. Like I said, I will have to see when I get in that area of the build. Thanks for all of the info guys.
I know this may need to go into another area of the forum, but what about closing off the vents altogether? Will that cause an issue on the A/C and heater? You talked about the vents were easy enough to remove so it can be cleaned out. On the A/C trucks the drivers side does not have a vent from what I have read. Not sure, yet. I may make a delete plate so the passenger side can be removed and cleaned out if closing them off will not matter. The drivers side is also a concern if it does not have one. I know I may be asking to many questions on this since I have not started on the restoration yet, but the more info I have before I start will be an advantage on my part of the time of the restoration. When I was restoring my 1985 Silverado I ran into a lot of issues and had to make a lot of changes and that takes a lot of time unless you may know what to look for when your doing the restoration. I am also going to put a 2004 5.3L with 4L60E trans in this rascal just like the '85 has. great communication with you guys. Keep the info coming.

[Mike C]

The rust behind the blower motor is caused not so much by trash in the cowl but there is an inner brace that is right behind the sheet metal. And it looks like they didn’t have a way to get the EDP primer or anything else between the two. Therefore it was bare metal on bare metal. The brace is 1/4” or so while the sheetmetal is 20ga. Therefore the sheet metal rusts out faster than the brace. I just did some of this repair on my kids Jimmy project and I will post some pics of that today or this weekend.

[COOP3726]

Thanks Mike C. What was the brace for and can it be done away with?

[Getter-Done]

Nice background story.

[COOP3726]

Thanks, Getter-Done