72 C20 factory air conditioning restoration

[540ChevyC20]

Hi All,

Looking to re-fit the factory a/c to my 1972 C20 BB after completing an engine swap. I'd like to keep the setup looking as factory as possible, going with modern parts where it makes sense. The new engine won't allow me to use the original compressor setup due to it having much taller valve covers, so I was thinking of instead using something like this:

https://www.originalair.com/gm-engin...tment-upgrades

I think I'd want to plumb this in to the existing air box and evaporator - here's a couple of pics of what I removed from the truck. I believe a previous owner has already changed the setup from factory as all photos of seen of the stock setup look different.





I don't know much about a/c but am keen to learn. If anyone is able to help me figure out how to make this work I'd really appreciate it!

Grant

[HotWheelsFan]

You should be able to retrofit modern A/C components to your existing evaporator and use your original evap housing. I don't know the company or how well their systems work. From a 5 min glance at the website link, I don't see any negatives that jump out. I'm sure they have their recommended parts to use with your evap and with modern compressors and refrigerant pressure regulation, it should be a nice addition to the original A/C interior look.

R12 and r134a systems use different types of oils and the oils do not mix. Evap can be cleaned with solvent type of cleaners (A/C system cleaners are available) and should have no problems.

Bob

[MARKDTN]

That looks like a later (cycling style) square body accumulator and evaporator. The A6 compressors used to be great, but now the Sanden style like your retrofit kit are a better way to go. I think you are on the right track, but your system is not stock 67-72 so you probably can't just order hoses in a kit. You will likely have to have custom hoses made, but some of the better auto parts stores can make them or you can order them online.

[PbFut]

What did you do to the rockers requiring the taller valve cover? Just curious.
If you can, I'd change the covers and keep the original look A6 compressor. To me, it's a better look. My valve cover (edelbrock) interfered with the adjuster arm on the rear mount. Some minor grinding of the arm corrected the problem. It was not so much as to cause concern for strength.
I am just starting on this same journey on my 72. All of my system was in tack so it makes things a bit easier. Purchased a new A6 with 134 oil in it as the old compressor was froze up. Also picked up a new drier. The aluminum tubes clean up nicely with sos and a wire wheel. You can pick up a system cleaning tool for pretty cheap. Get plenty cleaning fluid. Flush everything to get any dirt and especially old oil out of the used parts you are using. Harbor freight has a o-ring kit with the correct green material compatable with 134 that seems to fit well. Admittedly, I have little knowledge of AC systems so I am learning as I go and sure to make mistakes. Good luck on your project. I will be watching and learning.

[mrein3]

Originally Posted by 540ChevyC20

...snip...

I don't know much about a/c but am keen to learn. If anyone is able to help me figure out how to make this work I'd really appreciate it!

Grant

I re-habbed a stock system a few years ago. I put a stock system in a truck that wasn't shipped from the general with AC. I did convert it to R134a. You can skip a lot of the stuff I did but some of the general procedures will come in handy. Like what to flush the re-used components with. How to switch from one oil to another in the compressor. How to evacuate the system. I hope it helps.

http://67-72chevytrucks.com/vboard/s...d.php?t=478564

[540ChevyC20]

Originally Posted by MARKDTN

That looks like a later (cycling style) square body accumulator and evaporator. The A6 compressors used to be great, but now the Sanden style like your retrofit kit are a better way to go. I think you are on the right track, but your system is not stock 67-72 so you probably can't just order hoses in a kit. You will likely have to have custom hoses made, but some of the better auto parts stores can make them or you can order them online.

Yes, I was doing some research last night and it looks like a '77 onwards accumulator has been used in place of the original drier/receiver. The case itself does appear to be the original '72 item according to the decal on it. The case needs rebuilding, or I need to buy a repro - Ecklers makes one but I don't know what it includes (diverter door etc?). So I think what I need to do is go back to the '72 style evaporator and drier. Thoughts?

[540ChevyC20]

Originally Posted by PbFut

What did you do to the rockers requiring the taller valve cover? Just curious.
If you can, I'd change the covers and keep the original look A6 compressor. To me, it's a better look. My valve cover (edelbrock) interfered with the adjuster arm on the rear mount. Some minor grinding of the arm corrected the problem. It was not so much as to cause concern for strength.
I am just starting on this same journey on my 72. All of my system was in tack so it makes things a bit easier. Purchased a new A6 with 134 oil in it as the old compressor was froze up. Also picked up a new drier. The aluminum tubes clean up nicely with sos and a wire wheel. You can pick up a system cleaning tool for pretty cheap. Get plenty cleaning fluid. Flush everything to get any dirt and especially old oil out of the used parts you are using. Harbor freight has a o-ring kit with the correct green material compatable with 134 that seems to fit well. Admittedly, I have little knowledge of AC systems so I am learning as I go and sure to make mistakes. Good luck on your project. I will be watching and learning.

The engine is now a 540 BB Chev with Brodix aluminum heads, a big mechanical roller cam and associated roller rockers, so standard height valve covers are out of the question. Like you I want the factory look, but the compressor is one area I'm prepared to make an exception for ease of fitting and performance.

[540ChevyC20]

Originally Posted by mrein3

I re-habbed a stock system a few years ago. I put a stock system in a truck that wasn't shipped from the general with AC. I did convert it to R134a. You can skip a lot of the stuff I did but some of the general procedures will come in handy. Like what to flush the re-used components with. How to switch from one oil to another in the compressor. How to evacuate the system. I hope it helps.

http://67-72chevytrucks.com/vboard/s...d.php?t=478564

Thank you! Yes, I'd seen your post a while back when I first started thinking about refitting the a/c - I'll give it another read.

[Jason Banks]

It looks like your truck has an Old Air Products Evaporator Conversion kit installed:
https://www.oldairproducts.com/produ...t/default.aspx

I put one in 20 years ago and it worked great.

[Jason Banks]

[540ChevyC20]

Originally Posted by Jason Banks

It looks like your truck has an Old Air Products Evaporator Conversion kit installed:
https://www.oldairproducts.com/produ...t/default.aspx

I put one in 20 years ago and it worked great.

Thanks Jason! That certainly solves the mystery, it looks like that's exactly what was done. The evaporator still looks in remarkably good condition so I think I'll just re-use it. I believe the next step will be to contact Old Air and see what compressor and ancillaries they recommend to run with that setup.

I'd also like to either freshen up or replace the blower/evaporator box as it's rusty on the back and the diverter flap rubber seal has perished. Has anyone had experience with doing this, or working with vendors that do this? I see Original Air does offer a rebuild service.

[Jason Banks]

I lightly sanded my box down and used automotive clearcoat on it. Looks great.

I think in the past I had used some aerosol clear and it looked great too.

[dmjlambert]

Originally Posted by 540ChevyC20

Thanks Jason! That certainly solves the mystery, it looks like that's exactly what was done. The evaporator still looks in remarkably good condition so I think I'll just re-use it. I believe the next step will be to contact Old Air and see what compressor and ancillaries they recommend to run with that setup.

I'd also like to either freshen up or replace the blower/evaporator box as it's rusty on the back and the diverter flap rubber seal has perished. Has anyone had experience with doing this, or working with vendors that do this? I see Original Air does offer a rebuild service.

I recommend doing it yourself. I had Original Air do the box restore and in my opinion it was an incomplete job, so I had to take it apart and do the second half of the job myself. They did a good job making the outside look good and cleaning it up, but they were not interested in the door or rubber or patching holes in metal. Here are details of my experience with it: https://www.67-72chevytrucks.com/vbo...d.php?t=790246

Treat the rubber tube that goes between the evaporator box and blower motor with care and don't lose it. It is not reproduced and as far as I know would be somewhat difficult to fabricate. If it has any splits you can fix with superglue and spread some black RTV on top of the superglued crack.

[540ChevyC20]

Originally Posted by dmjlambert

I recommend doing it yourself. I had Original Air do the box restore and in my opinion it was an incomplete job, so I had to take it apart and do the second half of the job myself. They did a good job making the outside look good and cleaning it up, but they were not interested in the door or rubber or patching holes in metal. Here are details of my experience with it: https://www.67-72chevytrucks.com/vbo...d.php?t=790246

Treat the rubber tube that goes between the evaporator box and blower motor with care and don't lose it. It is not reproduced and as far as I know would be somewhat difficult to fabricate. If it has any splits you can fix with superglue and spread some black RTV on top of the superglued crack.

Thanks, yes after reading your experience I've decided to do it myself. The steel is rusty but I don't think there are major holes - I'll get the wire wheel on it very gently and clean it up, see what it looks like. I'm sure I can repair minor holes. The diverter flap rubber is mostly intact with the exception of a small missing piece which I figure I can mend somehow. I live in Austin, and the truck won't be driven in winter so I doubt that diverter will move much, if ever.