I have a '68 SB AC car. I have recently replaced the engine with a 383. I want to rebuild the AC, but I have many questons...and have little experience with AC components. I'm hoping someone can help answer my questions. TIA

I would like to rebuild the AC using R134a as the refrigerant. The system was working when it was parked about 4-5 years ago. The car was parked in a nice clean garage, so I expect the system is clean. However, when I had the original engine removed all the AC hoses, condensor, evaporator, and compressor were removed from the car. The engine was removed back in March. Since the evaportor was not plugged does that mean it may no longer be any good, since it was exposed ambient moisture?

I want to use R134a, since it is easy to get. Can I use the stock replacement hoses with R134a? How about the condensor and drier, can I use the stock replacements with R134a? My condensor and drier look good externally, can I reuse them? Is it possible to have these original components tested prior to installation?

I would like to replace the compressor with a polished aluminum unit to match the rest of polished engine components. Is there a recommendation for an aftermarket unit. I have also been told some of the new aftermarket units are more efficient and have less drag on the engine...true?? One of the aftermarket compressors that I have seen is Sanden...is this a good unit? Is there a particular model or style that I must use?

 

The evap and condensor should still be good. A flush is a good idea though. Use the special AC flush, even though it is expensive.

Any AC hose you buy these days is R134a compatible. No problem there.

The driers you buy now are R12 and R134a compatible (same part).

The Sanden 508 is a very popular upgrade. Compared to the A6 it is much smaller, weighs much less, cools the same and uses less gas. A win-win-win-win.

I'm currently in the process of swapping the A6 for a Sanden 508 on my 71. I can finally get to number 2 & 4 spark plugs. Woohoo! I see polished Sanden 508 's for less than $250 and natural finish for under $200.

 

Does anybody know of kits featuring the sanden compressor where you use the rest of your gm components instead of replacing the whole darn thing? I think my stuff inside the cab and the condensor are all right. I just need hoses and something to replace the vir or do I?

 

That's what I'm doing. Sanden 508 with everything else stock GM. Once I'm done I'll post pics and a write-up on my webpage. Have to get the engine running to go and have the custom hoses done. Meanwhile, here are some teaser shots:

 

I just rebuilt my A/C System, which was in similar condition to yours. I will try and guide you along. If I miss anything you may have had a question on let me know.

First off check your hoses for any cracks. If you see anything that remotely looks like a crack it should be replaced.

Compressor: If you are wealthy, replace the compressor. So much can go wrong with it, worst being siezed. If your not wealthy, your more like me. The best thing to do is refurbish your old compressor. A good way to start is with a "Shaft Seal" kit which can be purchased from your local auto parts store. When reintalling the compressor, be sure to put 1/4 the PAG oil necessary in the suction and discharge side.

Liquid Line: Should be Ok, check all metal lines for cracks, I had one. The Vette A/C System should be an "Orfice Tube" Setup. Alot of guys complain after doing the A/C conversion that their A/C is slight warmer then their newer cars. The best way to cure this is to install a VOV (Variable Orfice Valve). Without getting into detail, you have to replace the orfice valve anyway, so replace it with a VOV.

Accumulator: Its shot. If you use it your A/C will not function properly. Among its duties of collecting A/C it also collects any moisture in the lines... hence a system open that long will have a hell of a lot of moisture in it.

Evaporator: should be alright, .... you better hope so, its expensive.

Condenser: unfortuantely you cannot test your condenser for leaks because you lack the proper equipment. So the best thing you can do is visually inspect it, and the be sure to straighten out any bent fins. Bent fins can cause your vehicle to overheat, not to mention it will hinder the cooling capabilites of your A/C system

O-Rings: All O-rings need to be replaced with the GREEN ones for 134A Systems. Make sure you lubericate them with MINERAL OIL before installing them on the tubes. There are quite a few, take your time to replace all of them.

Fittings: You have to switch your fittings over from R-12 to 134A.

When you put you system together the key is to TAKE YOUR TIME; the pipes are all THIN aluminum and they bend, crack, and break very easily.

After the system is put together, the best way to make it work, and make it work well is to take it to a professional that has a A/C Machine. The system needs to be evacuated to 500 microns for 30 minutes to get out all the junk and moisture and air. Then the proper amount of A/C 134A, and PAG Oil needs to be added. Never use anything but straight up 134A. Stay away from those one can solves all problems oil, refridgerant, dye.... they are junk. The best thing to do is add the correct recommended amount of PAG oil, Refridgerant, and if you would like 2oz of dye. The dye is not a bad idea. It helps you solve leakage problems if you were have any in the future... which you shouldn't .

I know this sounds like alot of work, but its really not all that hard. Good Luck with your project, I hope this helps,

Dan

 

A given amount of oil should be added to each componant, evaporator coil, condensor coil, and comp. if it does not have the correct amount of oil from the factory (comp.). So if you plan on bringing it to a pro do not fully tighten the hoses.

 

It is possible to put in a small light compressor that uses less HP.

ND 6P (similiar to Sanden 508) w/ custom brackets & hoses to 77 Corvette factory A/C.
http://ganeys.home.sprynet.com/77ACs.JPG

Currently changing to Sanden 508 in the SS to factory A/C.
.

 

Interesting - I will be performing a similar upgrade in the near future.

It appears the Sanden 508 has some strong benefits. Does the Sanden 508 compressor need special brackets for mounting, if so, can these be purchased from Sanden?

Thanks!

 

 

Keep in mind that the original system increases the value of a 68-72 in the neighborhood of $5,000.00. If you decide to go with the modern system ( a good move in my opinion), keep every last original piece you remove, especially the the big long valve assembly (STV) bolted vertically on the evaporator case and the hose/muffler/manifold assembly.

I rebuilt mine original using a stock compressor, adjusting the STV for r-134a, found a used hose assembly that needed new hoses ($600.00!), and replaced the drier. I had to find all the brackets as well. Works great now, but I sure wish the previous owner(s) had kept that stuff! I do like the fact that it doesn't cycle the compressor clutch, but that's a minor issue.

One more thing. The fiberglass hoods tend to absorb the light refrigerant oils, so I'd advise you to make a shield (stock on the later ones) to prevent that. My original 427 hood fits perfectly, but has a 6" oil spot that soaked all the way through to the paint over the years. I'm slowly but surely getting rid of most of the old oil using laquer thinner on both sides, then I'll epoxy seal the area and paint. Good luck with the project!

Hans

 

Thanks for all the responses. Dan, thanks for write up...I found that to be very useful. zwede I look forward to reading your write up too.

zwede, did you have any issues with the length of the stock hose to the Sanden compressor, since the compressor is shorter? What is your source for the Sanden 508?

Dan, does the VOV valve replace the original POA valve? Is there any installation gotchas with installing a VOV valve? Will in mount in the same location as the POA valve? Is there more than one type of VOV valve or is there one that is specific to a Corvette? Lastly, for clarification, is an accumulator and drier the same thing?

Thanks everyone.

 

I just received my Sanden 508 and bracket from Hot Rod Air. I hope to start the conversion this weekend. The bracket is out of the complete conversion kit they sell. I talked to them and they said the conversion requires a new accummulator and orfice tube and of course custom hoses. The quality of the brackets is excellent. I'll keep everyone posted on the fit. I plan to use Aeroquip stainless braided A/C lines since I work at the plant where it's made. From talking to street rodders the Sanden should be quieter and require less horsepower.

 

I will not use the stock hoses as they are the wrong length. I'll also need some charging ports. There's a place nearby that makes custom hoses while you wait. Once the car is running I'll take it there and see what they come up with.

 

NAPA can make A/C hoses also.

 

1. Glad I could be of help to you. Right now you have a fixed orfice valve. It is located just after your Liquid Line. The purpose of the valves is to stop the flow of liquid refrigerant to the evaporator and to drop the pressure from high pressure to low pressure. Under this low pressure condition with the evaporator semi-flooded (about 60%) the evaporator/refrigerant can take on latent heat. This will cause the liquid refrigerant to evaporate into a gas once again. The gas will move on to the accumulator. Any "liquid" refrigerant that did not evaporate during the process will "accumulate" in the accumulator, and then the rest of the gas refrigerant will move on to the compressor. The compressor will compress and pump the gas causing it to become a semi liquid/gas that moves to the condenser where it becomes a high pressure liquid. And the process continues. This is really lengthy and un-nessary explanation on how it acutally works, but I figured it will help if you have a problem after the system is installed.

Now, because of your FOV (fixed orifice valve), only a fixed amount of liquid refrigerant can move past the liquid line an onto the evaporator. If you have a really cold day and you put too big of an orfice tube (anything other then stock) you will totally flood the evaporator, and chances are it will freeze like a block.... the refrigerant would never evaporate into a gas, it would move to the accumulator, flood that too, and then after thats flood it would move to your compressor. As we know you cannot compress a liquid, so you would destory your compressor. On a hot day, with your stock valve,... corvette owners find that it barely cools the car.

A VOV (Variable Orfice valve) varies the amount of refrigerant that it will allow to the evaporator to prevent the above! So you have awesome cooling all the time with no failures. The best place to get one is from your local Chevy Dealership. They should have them on the shelf, but only a good tech will know they exist! So if you don't get the answer your looking for ask again.

Or you can just get one from www.ACKits.com The quality is good on the VOV's but stay away from their accumulators... there cheap.

2. Theres no catch to intalling one of these, just unscrew your liquid line, pull out the old on, slide in the new one. Be careful the VOV is fragile, and you need to put a little force into it to get it to slide back in the tube.

3. The VOV installs in the same spot as your previous FOV. Just slid out the FOV and slide in the VOV. Make sure you lube up the O-rings on both the VOV and the aluminum tubing with Mineral Oil.

4. An accumulator is different from a receiver-dryer. They do similar things but in different ways. You can only have one. In your case the proper terminology is accumulator.

Hope this helps,

Dan

 

No, no, no!!!

The 68 has a TXV system. Thermostatic Expansion Valve. THERE IS NO ORIFICE TUBE. That came much later.

 

Yep, he's right. Most folks that upgrade these old cars switch over from the old system to the one Dan's talking about by removing all the old valves and compressor, then adding an orafice tube, cycling switch, and modern compressor.

Also, before GM switched over to the cycling type systems, they use a third system starting in '73 to about '79(?). Hope this helps.

Hans

 

The TXV is a better system as long as it is serviced corectly.

 

Again, thanks for all the responses. Dan, I appreciate your response to my questions...the explanations are very helpful. I think I have almost all the info I need to tackle this project myself. However, one more question...

If I switch to a VOV do I need to add a cycling switch or does my old system already include it?...I think I understand the purpose of the switch...to keep the compressor from continually running and building excessive pressure.

Thanks.

 

Hello,

Sorry for any confusion I might have caused. You have a TXV (Thermostatic Expansion Valve) Type system with a Receiver-Dryer; this is according to ZWEDE. Not an Orfice Tube Type. I have worked with both systems, but MY 82 Corvette has an Orfice Tube System. Thats what I thought you had; my mistake. You don't need a VOV at all. It doesn't apply to your system. Again, sorry for the confusion.

What you can do is follow the FIRST post I made, with the exception of the part about the VOV and you should be in good shape!

Ill give you a quick list,... just in case I may have confused you.

1. Check all lines and hoses for any cracks
2. Replace your compressor or use the old one and replace the shaft seal
3. Replace the reciever-dryer
4. Upgrade to the new O-Rings (the green ones) for 134A, making sure to lubericate them with MINERAL OIL prior to installation
5. As new components are installed add the specified amount of PAG oil to each component. (I think my system took 8OZ of oil, but mine is different then yours so you may take a different amount; point is I put 2oz in each component)
6. Carefully check condenser for cracks, or bent fins, and straighten any bent fins.
7. Tighthen all fitings carefully
8. Evacuate System to 500 microns for 30 mins
9. Add straight refrigerant. (No sealer or oil)

I hope this helps,

Chevymans77, Zwede, Wrencher, Vette79,

If I missed anything please let me know.

Dan