So...what are you using instead?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeah, I am curious too!

I'll tell ya, if the old r12 valve isn't optimum, it is sure working pretty good in my car.

It was only 80* ambient the other day though. I am wondering how it will do on a really hot and humid day.

I won't have to wait long to find out!

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-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

Yeah...I would say your next step wouldn't have anything to do with the system itself, but would focus on reducing the system's workload by means of good quality window tinting (not the cheap film that turns purple in a couple years) and better insulation.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

There are two basic types of expansion valves, the externally equalized (which has the pressure sensing line that goes to the outlet of the evaporater, and the internal equlalized, which sensis the evap pressure on the inlet of the evap. The purpose of the expansion valve is to meter the refrigerant into the evaporator, to maintain a "almost flooded evap". it does this by comparing pressure and temp of the refrigerant. The externally sensed valve is better at controlling this, because it senses the presure and temp at essentially the same place in the system. The adjustment in the end of the valve is to adj the "superheat". It does not adj pressure. Every A/C evap needs a certain amount of superheat to allow the coldest evap possible, with out allowing liquid refrigerant to get back to the compressor.


Dan, as for the regulation about HP coutoff switches. I don't know where to look that up, maybe on the EPA website, about retrofits. It might be listed in the same place that says, any system retrofitted to a refrigerant that contain R-22, must use "barrier" style hoses. I learned this stuff going to different schools and training sessions, but that was maybe 15 years ago. I have been to numerous "schools", on A/C and refrigeration.
PS I am certified under part 608 and 609.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Well, so much for making changes to the original valve. Thanks for clearing that up.

As far as what valve I am using, it is the internally equalized type. All my underhood plumbing is new and there is nowhere to connect the old valves pressure line. Sure I could have a fitting welded on to the suction hose fitting, but I just decided to keep it simple with a valve set for r134. I am using a sanden as well.

As an A/C guy myself it really nice to hear correct info from time to time. Charlie is right on.
I'd also like to add that if your expansion valve is external psi sensing, the psi sensing tube must be hooked up and can not be plugged.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Guys this is great info. Thank you.

So if I wanted to get rid of the oem expansion valve with all of the associated capillary tubes to "clean things up" under the hood, and get an actual 134a compatible valve, I could:

1) find a way to plumb a 134a internal sensing exp valve into the the high pressure line at the firewall.

2) plumb in a external sensing pressure valve for 134a, assuming there is such an animal. (I'm not sure there is going off of what Bren67 said)

??

Is that about right?

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-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

I wouldn't do this, if I were you. The OE expansion valve works very well, and...really, now, does its appearance bother you that much?
You could put in an H-style (block) valve if you really wanted to. They make them with threaded fittings. But it'd involve a lot of tube, fitting, and flange reworking, and for what real benefit? Again, I think you'll see a much larger, more cost-effective improvement in system performance by going in for some quality window tinting (I like the Llumar films; I've had 'em on the Lancer and the 164 for years and they've held up very well).

I'd also look at insulating the space between the headliner and the metal roof panel, and the next time you've occasion to pull up the carpet, improve the insulation there, too, and behind the back seat.

I'm still coming up zero looking for R134a-specific expansion valves. The 1977 Dodge Aspen and 1991 Dodge Spirit (w/R12) and the 1999 Dodge Neon and numerous other models (w/R134a) all use the same block-style expansion valve, a Four Seasons #38849. OK, that's aftermarket, but the '91 Spirit (w/R12) and the '95 Spirit (w/R134a) also got the same expansion valve (#4176 999) from the factory. So I really wouldn't spend too much time or effort chasing down an R134a-specific expansion valve.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

No, honestly it really doesn't bother me too much. I am going to do an upgrade on my 73 /6 dart next, and I was thinking of using that one as a guinea pig. But I agree too, if it ain't broke dont fix it.

Funny you should mention the insulation. Right now the car doesn't have any carpet or jute in it. I am getting it ready to weld in the subframe connectors, which I aim to pick up from US Cartool at Carlisle this year.

Without the carpet and the jute, that floor gets HOT!!!

Dan this may be a stupid question, and sligthly off topic for the thread, but I always wondered why tinting windows a dark color would cool the inside of the car, rather than absorb heat and make it hotter. ??

Thanks

CE

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-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!

It does seem counterintuitive, but the dark appearance is only one part of what's going on. There is an enormous range of different tint films on the market. Depending on the dyes and/or metallic coatings in and on the film, they block various levels of visible light, UV (which causes fading of interior materials) and/or infrared (=heat). If you go for window tinting, it's worth buying one of the relatively expensive high-tech metallised films. Mouse around on the Llumar site I linked; they have a pretty good PDF that gives the specs on a bunch of their films.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.