Air Conditioning/Firewall question

[79SierraGrande]

Does anyone know if the firewalls on a 73-80 square body are drastically different on a A/C vs. non-A/C truck? My current build is a non-A/C truck from the factory and I would like to add A/C to it but not any of that vintage A/C stuff some companies sell. So if the firewalls are pretty close to the same as far as the holes for the heating/cooling systems then I would love to do it.

If they're not and I'll need to do a good amount of fabrication anyway then I have the option of taking all the A/C components out of a 1991 Suburban a friend of mine has that he said I can have. That would be including everything on the interior side of the firewall too, even the controls in the dash.

Thanks in advance for your help!

[79SierraGrande]

My current build is a 1979 GMC Sierra Grande 4x4 SWB.

[Sartobuilt]

The holes are in different locations. You can cut and patch to make it work. If I had to convert one, I would replace the firewall section with the one from the donor.

[79SierraGrande]

The holes are in different locations. You can cut and patch to make it work. If I had to convert one, I would replace the firewall section with the one from the donor.

That's a good idea, Sartobuilt! I will definitely see if that may be possible to replace that section of the firewall on my truck with the one from the 1991 Suburban. I'm not sure how different they are but that just might work. I'll have to see if I can get my brother to take a look too and see what he thinks. He's a mechanic by trade and a far better welder than I am.

[Jason S]

I'm not sure how different they are but that just might work. I'll have to see if I can get my brother to take a look too and see what he thinks. He's a mechanic by trade and a far better welder than I am.

 

Welding in a portion of the firewall off the Suburban, as Sartobuilt said, is a good idea. Many years ago I converted a non/ac truck to factory a/c, but just cut and patched the areas necessary- I wish I had taken photos. 

The blower motor will physically be in the same location, so no cutting needed. Otherwise, on the non/ac cab, a portion of the firewall will need to be cut at the location of the evaporator and a portion of the firewall (over the area where the original heater core was located, adjacent to the evaporator hole) will need to covered.

The patched and cut areas will be covered over by the a/c plenum under the hood and by the a/c ductwork inside the cab. 

Keep us updated and take lots of photos.

[roundhouse]

We just cut a new hole and patched over the old one
It can't be seen
Lot easier to screw a metal patch over the hole than weld it


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[Captkaos]

Here are pics from Sartobuilts firewall for AC for reference.  If you have a donor you are ahead of the game to use the factory setup.

http://forum.73-87chevytrucks.com/smforum/index.php?topic=21690.msg179454#msg179454

[79SierraGrande]

I'm not sure how different they are but that just might work. I'll have to see if I can get my brother to take a look too and see what he thinks. He's a mechanic by trade and a far better welder than I am.

 

Welding in a portion of the firewall off the Suburban, as Sartobuilt said, is a good idea. Many years ago I converted a non/ac truck to factory a/c, but just cut and patched the areas necessary- I wish I had taken photos. 

The blower motor will physically be in the same location, so no cutting needed. Otherwise, on the non/ac cab, a portion of the firewall will need to be cut at the location of the evaporator and a portion of the firewall (over the area where the original heater core was located, adjacent to the evaporator hole) will need to covered.

The patched and cut areas will be covered over by the a/c plenum under the hood and by the a/c ductwork inside the cab. 

Keep us updated and take lots of photos.

Thanks, Jason! I appreciate the great info! I will definitely keep everyone updated and take lots of photos. I'm a journalist and photoj so I love taking pictures. Sometimes I probably take too many. Haha!

I'll be sure to post some pics of the donor Suburban under the hood/firewall and dash controls early next week when I'm out at the shop again. I'll take some of build truck's controls and current firewall also even though I'm certain you probably already know what the pictures are going to look like.

[79SierraGrande]

Here are pics from Sartobuilts firewall for AC for reference.  If you have a donor you are ahead of the game to use the factory setup.

http://forum.73-87chevytrucks.com/smforum/index.php?topic=21690.msg179454#msg179454

Thanks, Captkaos! I love your build truck with the turbos if that was yours!? I can't remember now. Now I'm tempted to add some of those turbos to this LS3 engine I want to put in my build truck. I'll check this thread out. Yes, I do have a Suburban to I can steal all the A/C components out of for free. It's either a 1991 or 1992. My friend bought it just to steal the interior out of it and all the doors. Anything else is fair game. I'll be posting some pics of the firewall and inside controls of the Suburban early next week as well as my non-A/C build truck's firewall and controls.

Thanks for the help.

[HAULIN IT]

If you have a complete donor truck...it's a straight forward, nuts & bolts swap with the exception of drilling a few holes, closing a 1/8" dia. hole or Two & the mentioned 4" x 8" or so rectangle...which is the hole closest to the blower motor in the picture Capt. posted.
Sartobuilts (the photos Capt. posted) was doing the opposite...going FROM A/C to non-A/C so he was closing off the inboard hole & cut the one you will be patching.

There is NO need to cut any part of the donor firewall to weld in, unless you want to use it to cut that small rectangle out for your patch. The patch (all but a very little bit to the inboard side of the blower) is hidden by the new box, so it really doesn't have to be all that much...basically flat & sealed is what counts.

What I've done is use a large piece of heavy paper/light cardboard & make a template (rub over the holes with a dirty finger & use a marker to locate the exact center of the holes) of the donor firewall. Go to your truck & match it up to the holes that match...some do. Hold the template in place with the existing screws & transfer the center of the new needed ones with a punch & drill. My Two Cents, Lorne

   

[79SierraGrande]

If you have a complete donor truck...it's a straight forward, nuts & bolts swap with the exception of drilling a few holes, closing a 1/8" dia. hole or Two & the mentioned 4" x 8" or so rectangle...which is the hole closest to the blower motor in the picture Capt. posted.
Sartobuilts (the photos Capt. posted) was doing the opposite...going FROM A/C to non-A/C so he was closing off the inboard hole & cut the one you will be patching.

There is NO need to cut any part of the donor firewall to weld in, unless you want to use it to cut that small rectangle out for your patch. The patch (all but a very little bit to the inboard side of the blower) is hidden by the new box, so it really doesn't have to be all that much...basically flat & sealed is what counts.

What I've done is use a large piece of heavy paper/light cardboard & make a template (rub over the holes with a dirty finger & use a marker to locate the exact center of the holes) of the donor firewall. Go to your truck & match it up to the holes that match...some do. Hold the template in place with the existing screws & transfer the center of the new needed ones with a punch & drill. My Two Cents, Lorne

 

Thanks, Lorne! I really appreciate the information! That sounds pretty easy then. I'll be posting some pics this week of the firewall on my build truck and the donor Suburban for documentation and in case anything is funky then everyone can see what I'm dealing with. I'll keep you posted.

[79SierraGrande]

Here are the photos of the donor Suburban my buddy has that I can steal the A/C components from. One mistake, I thought it was a 1991 but it's actually a 1989 I guess. I checked out the registration in the glove box today when I was out at the shop.