when the automotive A/C expert technician told me I was missing something on my car, (the low side charge valve) I assumed he was correct. NOTE...he is not an early A-body expert..obviously.
Obviously. He was wrong about no low-side port (it's the one on the head), he was wrong about it not having a Schraeder valve (the low-side port on the
head does indeed contain a Schraeder valve unless someone has removed it, in which case all that's needed is to install a new valve core because the port body is already threaded to accept it) and he was wrong about your compressor "missing" the EPR valve (no such valve was used in A-bodies until 1974).
1965 was the first year an integral heat/AC/defog system was available on the A-body, and it was not available until the middle of 1965 production. The information on that system was not included in the 1965 service manual; a separate supplemental manual was published to cover it, and it appeared in entirety in the 1966 factory service manual.
The bottom line....the system is correct.
Yes.
However I was convinced the proper solution was to tap and insert a Shrader valve in the rear fitting, install the EPR valve, charge the system with R-134 and have cool air.
No. See above re Schraeder valve. Do not install an EPR valve in the compressor; it'll
reduce your system's performance. Do not expect to charge this system with R134a and get much in the way of effectively cooled air. The A-body system as designed and built the first few years was marginally adequate to cool a Dart or Valiant sedan or hardtop. It was inadequate to effectively cool a Barracuda or a station wagon; the long body of a wagon or the giant backglass of a Barracuda turns the car into a solar oven the A/C just cannot keep up with. This was with R12; when you charge an R12 system with R134a you lose some cooling efficiency especially under high-demand conditions (low or zero road speed, low engine speed, real hot days).
The best upgrade you can make is a parallel-flow condenser. This will make an enormous improvement in the efficiency and performance of your system regardless of what refrigerant you use. A side benefit is lower head pressure (and therefore lower torque load on the engine from the compressor) due to lower flow restriction.
Reference:
parallel-flow condensers
and [ame=http://www.ackits.com/testresults/alttest.pdf]comparative refrigerant tests under standardized conditions[/ame] -- look at the difference in performance between a serpentine condenser like you have now, and a parallel condenser...with ANY refrigerant.
Also make sure you have a very good radiator fan. A six- to 9-blade fan of at least 17" diameter with a thermal fan clutch is the way to go, and you should have a fan shroud.
The other big upgrades have nothing to do with the workings of the A/C system itself: insulate the car! Find and seal all the holes in the firewall and floor pan (there will be many), take down the headliner and put insulation up there before reinstalling the headliner, insulate the door panels, and put quality tint (Llumar, for example, not the cheesy dark purple junk) on all the glass. This will dramatically reduce the "solar oven" effect that defeats even the best-working A/C system.
how does one charge the system...with the compressor turning or not turning.
If charging through the low side it's done with the compressor engaged (clutch cycling switch bypassed), the blower fan on high, all windows open, and the engine operating at a fast idle of about 1500 rpm. And because the low-side port is directly overtop the compressor's valves, you take particular care to make sure
no liquid refrigerant enters the compressor: you have the refrigerant container upright, you use long gauge hoses, and you just
crack the low side gauge valve. Liquid entering this port will cause physical damage to the compressor.
If charging through the high side it's done with the engine and compressor
off, and you can charge either as a liquid or as a vapour.
In either case, particularly when using a refrigerant other than what the system was designed for (e.g., R134a in an R12 system) it's best to charge by weight. Second preference is to charge by volume. Distant last preference (i.e., don't do it because it doesn't work) is to attempt to charge by looking at the sight glass or grabbing the low side line to feel it getting cold.
R12 or R134a are the only refrigerants you should use. Do not use the hydrocarbon-based "replacement" or "substitute" refrigerants (OZ-12, HC-12, RedTek, etc.). They work, but they're dangerous and illegal. Do not use the non-hydrocarbon "replacement" or "drop-in" refrigerants, either (Freeze-12, etc.). They work poorly and cause problems. R12 really isn't expensive; there's not much demand for it any more and your system really doesn't need that much of it. Go look on eBay and see the steady parade of NOS R12 cans!
Here is hoping the "expert" who didn't know what the hell he was talking about with regard to your system is at least smart enough to know that R134a is not compatible with R12-type refrigerant oil, and that a new filter-dryer compatible with the refrigerant you're using is an absolute necessity.
would allow me to "refresh the 134 occasionly as needed" using the readily available parts store 134 kits?
If your system requires periodic topping up, it has not been assembled correctly. Leaks are not normal.
