1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Here is a picture of a 1979 GMC 7000 with 4-53T equipped with A/C and fan clutch. This picture was on www.4btswaps.com "foxyboxy" forum.

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

These look to be the relevant pages for fan clutch stuff:

http://gmpartswiki.com/getpage?pageid=176194
http://gmpartswiki.com/getpage?pageid=176193
http://gmpartswiki.com/getpage?pageid=176192

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

I didn't think about the GM Wiki page, forgot there are some medium catalogs listed there. Looks like the first design used the same clutch for the 350 and 366, Hayden # is 2801. It has a four bolt pattern on the pulley and fan, looks real similar to the one in the picture.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Thanks Robert! Great help, the first design used on the 350 should be fairly common and easier to find. This gives me a good start.

David

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

You're welcome, credit goes to Devin for finding the parts pages. I'll have to bookmark that catalog. That clutch is also similar to one for a 454, # 2797. You might check the specs on them and see what the mounting dimensions are for the pulley and fan.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Here are pictures of progress. Got the cowl, roof, door openings, and rocker panels sanded, rear of cab to go then prime and paint.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Removed a hail dent from the roof. Installed new left and right doors. Took some adjusting to get them to line up correctly. The original doors fit terrible, I was in hopes the aftermarket doors might align better. In the 1979 era, fit and finish were not anything like today's standards. After some twisting bending and lots of adjusting I got them to fit slightly better than the original OEM doors. Time will tell how they hold up.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Made a little progress, transferred mirror mounting holes from old doors to the new. I used masking tape to make a template and then moved the template to the new door. I use multiple layers so it does not stretch when removed and reinstalled. Once the holes were all drilled (used a step drill bit to get a nice smooth hole with no stress risers) I then primed the holes.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

More progress:

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

More progress, I had good help, my sons Noah and Micah were great! Also pictured is my bride (Angie) and yours truly.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

More progress:

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Started putting the cab back together, cowl area is complete, driver side mirror mounts have been installed, once I get the passenger side done I will be working on the cab clearance lights.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Got the cab finished! Glad to have this portion of the rebuild done! Purchased a temporary 30 day tag so I could take it to town to have Air Conditioning lines made. When I started to pump the system down I remembered it was configured for R-12. Another trip to the parts store to get the R134A adapters.
I pumped AC system down, serviced with oil charge, then started adding the first can of Freon R-134A. Much to my dismay, I discovered I had fabricated lines that hooked the low pressure side to the discharge of the compressor and the high pressure side was connected to the suction. Some days you just cannot get it right! Hopefully I can figure out a easy fix as I am using the original GM style connectors on the compressor.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

The fun details, made a conformity sticker to replace the original. I had taken a good picture of it before removal. The sticker was originally printed on a paper label with a clear film over the top. Was able to get sticky project paper at Office Max and clear printable shipping label. I then recreated the sticker using Microsoft Paint, printed it and then cut the clear to fit with the required overlap. It turned out really good. The first picture is the original and the bottom picture is my re-creation.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

More progress. Got the Air Conditioning finished up. Made new hoses that connected the compressor output to the high side and the suction to the low side. Serviced with oil charge, and 4 cans of 134A. Presto, we have cold cold air blowing out the dash vents. Moving the temp control allows us to blend the temp as advertised. Next we installed the rain gutters over the left and right doors.

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Making some good progress! Were you able to get a fan clutch for the 4-53? I'm running R12 in my welding truck and pickup, got a decent deal on two cases a couple years ago. I installed one electric fan on my '84 to help with all the heat the 454 makes, it can get down to freezing with no trouble idling.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

I have not purchased a fan clutch and fan. I am still looking for one.

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Found this on ebay, correct for a medium duty with a 350. That bolt circle would fit on the 2797 fan clutch. Seems like the catalog might have been wrong, as a 2801 clutch is for a 366 and 427 that takes a larger fan. I'm betting this fan and the 2797 will fit your truck if the mounting dimensions are right.

https://www.ebay.com/itm/CHEVROLET-C...YAAOSwH-daKvZX

https://www.rockauto.com/en/moreinfo...793626&jsn=573

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Thanks Robert, I really appreciate your help!

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Robert,

My current fan has a 22" diameter. It also has seven blades.

David

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

You're welcome, we did our best to locate things when I worked at the parts store and that stuck with me. I look up my own parts before I go to the store to avoid unnecessary headaches haha. Seems like that fan would work, the 2" difference in diameter shouldn't hinder the cooling any I would think. The depth that the fan goes into the shroud is important for sure. The height of the 2797 clutch is about 3 5/8" roughly. The bolt spacing for mounting the clutch to the pulley/pump is 2.5".

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

I need to measure the depth to make sure I have room for it. I will take some more measurements and post the results.

Thanks Robert!

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Shortened the frame back to its original wheelbase (203 in).

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Been going through the brake system replacing wheel cylinders and hoses. I have also taken the opportunity to strip and prepare to repaint the Dayton hubs. I have new tubeless 11 - 22.5 rims and radial tires ready to be installed. I wanted to keep the original 9.00 - 20 rims, however radial tires for them were almost impossible to find and very expensive. I know in the long run the tubeless is a much better option.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Continuing to make progress on the brakes. Front brakes, master cylinder, and hoses are finished. The passenger side rear is ready to have the drum reinstalled and it will be finished.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

New front brake lines:

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Can anyone tell me what the sender on the Secondary fuel filter does? It has a single wire going to it. I assume it applies a ground when the pressure reaches a given threshold. I have grounded the terminal and do not get any light showing on the dash. I have reviewed the wire schematics and do not find any information about it.

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

On our 8V71 's at work it is connected to a circuit that allows the engine to stay running. No fuel pressure; shuts off. However those engines have a Woodward hydraulic governor. Yours does not. May also be used as a "run" circuit to send power to various things to signal the engine is running. It has been a while since I've had to mess with that engine. Pretty reliable.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Finishing up the last brake. Here is a picture showing my sons Micah and Noah learning how to reinstall the rear brake shoes. They were fascinated with how the brake spring installation tool worked. In this picture they are installing the lock rings on the brake shoe retainer castle nut.

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Can you post a picture and hopefully a part number of the brake spring tool you used?

When disassembling my C50 brakes I used big ass sheetmetal pliers but it was not fun.
Thank you.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Here is a picture. It makes spring removal and installation a breeze. No effort required.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Finished brakes, installed new rear transmission seal and parking brake shoes. Installed new front shocks, my sons Noah and Micah stripped and repainted the front and rear hubs and clamps. Installed new tubeless rims and tires (11.00R 22.5 radials) Next step is to acquire a bed and we will be ready to haul.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Drove the truck to town and got it inspected and licensed. The truck rides terrible with the new tires. The air pressure is 85 psi. The old bias ply tires rode much smoother. The left rear duels wobble just a bit, will have to loosen and re tighten them to see if I can correct. I sure hope the bed weight will smooth things out! Any ideas?

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Best thing to do is jack up the front/rear and spin the tires by hand and check for run-out. We had that happen on our old '79 Ford L8000 water truck at the fire department. The front wheels were actually worse, when I looked out the driver's door while rolling I could see the tire/wheel wobbling in and out. Local tire shop apparently never worked with Dayton wheels before. I'm actually going to look at a 1989 C70 cab and chassis next weekend if they don't sell it by then. Has a 366 and a 5+2, has the same wheels but it has 10.00-20 tires.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Thanks Robert, I will jack it up and check the run out. Hopefully that will fix the problem. I hope it is not a bad tire. I still need to get the A/C fan clutch installed. I am sure it will reduce load on the engine and noise. The current fan is fixed and very noisy. With a Detroit Diesel cooling is not much of a problem. I cannot imagine why GM did not make the clutch standard on this model. Thanks for all your input!

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

I am having trouble with my new Accuride de-mountable rims. The part of the rim that clamps to the wheel runs true. However the outer rim wobbles. It appears that when the welded the clamp ring to the wheel they did not have it square. Anyone else had problems with Accuride rims?

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Thanks for documenting this so well.

Were the AC donor parts from a pickup or MDT? I would like to add air to my crew cab.

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Find an experienced tire guy. It is part art, part skill to tighten clamp nuts so the wheel runs true.

1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

The parts were from both a C65 and 70's pickup. The evaporator and heater core are all the same. The parts that are unique to the 2 ton are the vent distribution in the dash and the mode selector control (no bi-level mode on the truck). I believe that a pickup unit would work, you would just have to use hose instead of the molded plastic parts to distribute the air to the drivers side of the dash. I am not totally sure as I was able to rob those parts from the C65. I know the heater floor distribution is different. I reinstalled my original heater floor distribution unit and it mated up with the pickup evaporator housing. The pickup condenser is very similar and can be made to work. The lines on it are aluminum where the C65 used steel. Hope this helps.

David

Re: 1979 Chevrolet C70 Conversion to OEM Air Conditioning
 

Thanks!