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Updating a '71 Pontiac

Vetteman61 on Sat July 19, 2014 4:29 PM User is offline

Year: 1971
Make: Pontiac
Model: Grand Safari Wagon
Engine Size: 455


I have restored a 1971 Pontiac wagon that still has its original 455. I have done quite a bit of research but I am not confident that I know enough to order the correct parts. The original cooling system has been removed and I plan to convert it to 134a. I have done research and I would like to change the original compressor (which needs replacing anyway) to a Sanden compressor. Vintage Air makes a bracket to make this swap very easy.

The original system used a POA valve, which I understand does not cycle on a '71. If I get a new Sanden 508 model compressor, will I need to replace the POA valve with a kit that replaces the POA with something that allows "cycling," such as the kit in this link:

When I switch the compressor, are there any other parts that may no longer be needed with a new, 134a, cycling type system, or parts that may need to be added?

Here is the list of parts I plan to replace:
POA valve kit (if necessary for new Sanden compressor)
New Sanden compressor
Dryer assembly
Evaporator core
Two new hoses (big and small)
Set of 0-rings
Expansion valve
Several cans of 134a freon

I have heard that a new, redesigned orifice tube is available that has been designed for use with automobiles that used to use R12 and have been converted to 134A. This tube is said to provide cooler air temps. Would this part be necessary for this system?


Edited: Tue July 22, 2014 at 3:40 PM by Automotive Air Conditioning Information Moderator

wptski on Sat July 19, 2014 5:25 PM User is offline

That site doesn't allow links to this site, so the moderator will delete it once it's seen here.

Edited: Sat July 19, 2014 at 5:26 PM by wptski

mk378 on Sat July 19, 2014 5:50 PM User is offline

You should consider a variable compressor such a the V7. It regulates the pressure internally, similar to what a POA valve does, and thus runs without cycling.

This would have been a TXV system not OT. The best way to run a fixed-displacement compressor on a TXV is to have an evaporator temperature sensor control the cycling.

Also, parallel flow condenser and make sure the fan clutch and shroud are good.

bohica2xo on Sun July 20, 2014 8:18 PM User is offline

The "POA eliminator" is not something you want to install in that car. Neither is a little compressor like the 508 sanden.

You have a 19 foot long, 7 foot wide car with more glass than two Tahoe's. That is a lot to cool. Back then GM engineered & built excellent A/C - it was an expensive option.

The original A6 compressor with the TXV & POA valves cooled very well. The A6 has a displacement of 12.6 cu in /rev. The POA valve kept the evaporator at a constant pressure.

There are a couple of ways to retrofit that system:

1) Keep the OEM style
This means re-calibrating the POA valve to work with 134a and replacing the A6 compressor with a fresh A6

2) V7 compressor
The V7 compressor has the same displacement as the A6, and incorporates evaporator pressure management. It is already calibrated for 134a
You would need to fabricate or modify a mount to fit the 455. The POA would be removed.

In either case, you want to install the largest parallel flow condenser that will fit in front of the radiator. A new fan clutch, and the OEM fan shroud should be installed. The original style receiver / dryer and TXV will work just fine.

The variable displacement V5 is very efficient once the car is cooled down, and has the capacity to cool that big greenhouse. 134a will do the job well if you have a good condenser, with plenty of airflow.

"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Vetteman61 on Mon July 21, 2014 8:38 AM User is offline

Thank you for your responses. I will not go with the POA cycling kit then.

Would it be possible to keep the POA (reset for 134), install a new parallel crossflow condenser, replace all other components with new of course and use a regular compressor like the S6 (regular meaning that they are not internally calibrated)? The reservation I have with replacing the old A6 compressor are two things: From what I've read (and my own experience) the A6s that are now available don't have the quality of the ones from years ago and also I have a goal of getting 20mpg on the highway from my car (I'm pretty close) and I've read newer styled compressors have less parasitic draw. The main reason, though, is that the A6 compressors don't seem to have the quality anymore.


Edited: Mon July 21, 2014 at 8:40 AM by Vetteman61

bohica2xo on Tue July 22, 2014 1:08 PM User is offline

I have no personal experience with the S6, and do not know the displacement. I have heard that they fit the A6 bracket well.

I would call the site sponsor (AMA) and ask Tim or Jack about this. They do some hot rod work in their shop, and since they are in Phoenix they know what it takes to cool a car.

Arizona Mobile Air 602-233-0090

If the S6 can support 45,000 btu/h it will do the job.

Mounting a V7 in the A6 bracket can be done with some fabrication. You would need the V belt clutch, mounted on a compressor from an S10.

Good luck with your project. Always nice to see the old stuff still on the road.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Vetteman61 on Sun July 27, 2014 3:31 PM User is offline

Thank you for the response and your help.

Vetteman61 on Mon July 28, 2014 11:57 PM User is offline

If I wrote what you read correctly then when I purchase a new receiver/dryer, I don't need to make sure the receiver/dryer is 134 compliant? The only reason I ask is (and I've read so much in such a short time I may be getting confused) that I think I've read several times I have to get a new receiver/dryer that is designed for 134.


wptski on Tue July 29, 2014 11:40 AM User is offline

Most anything in stock these days is for both R12 and R134A.

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