Time to drag out the paint gun.... new scoops for the Duster!
1972 Duster Build with my Daughter
- Thread starter Jim Kueneman
- Start date
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That's looking mighty fine. Love that hood
Nice, I have a set for a Duster I recently bought, I sanded them down, and primed them, just need to sand the primer, and shoot some black on them.
The
I just wanted to correct a misconception: the RV2 isn't really a "power hog", it just seems that way. The amount of shaft power needed to drive a compressor depends on the compressor's displacement, volumetric efficiency, isentropic efficiency, mechanical efficiency, all else being equal. Certain other factors affect this as well, such as how much oil circulates in the system. Less oil circulation results in improved efficiency, and compressors with sumps like the RV2 circulate much less oil vs "modern"* axial piston compressors. Overall, from published results, twin-cylinder compressors like the RV2 and York are actually more efficient vs axial piston compressors like the Sanden, Seltec, Denso, GM a6, DA6, etc, and other swash and wobble plate compressors.
The reason the RV2 (and York, Tecumseh, and to some extent the GM R4) has the reputation as a "power hog" is twofold. First, they DO use a lot of power, but in return you get a very high refrigerating capacity due to their large displacement combined with high volumetric efficiency. Second, this large effective displacement combined with a relatively small, inefficient condenser results in higher head pressures, which increases power usage. Similar displacement "modern" compressors actually pump less refrigerant due to lower volumetric efficiency (VE), which means they have less capacity but also lower head pressures and thus lower power input requirements. Another thing that I think contributes to this is that the two cylinders have large torque fluctuations per revolution compared to axials with more cylinders, so when the clutch engages against head pressure the immediate response is more noticeable.
If you're not concerned with a totally accurate restoration you may want to consider safely packaging and storing your original tube and fin R-12 condenser and installing a modern (no quotes) parallel flow condenser. Sites like UAC have dimensions for OE and universal parallel flow condensers. You need to watch for the tubes and mounts to make sure a given condenser fits in the available space, and you will want to make adapter brackets to mount it without modifying/hacking your original core support. Within the constraints of your original condenser or available mounting area, you want the biggest, thickest parallel flow unit you can fit. This is true even if you use R-12, and especially true if you use R-134a. A parallel flow condenser will reduce head pressure and provide more subcooling, which will increase system capacity and efficiency while actually reducing power consumption by the compressor. A win-win-win.
All that said, you are otherwise correct: The RV2 is simple, reliable, easy to rebuild, and HEAVY! Who cares? You don't have to hand-carry it wherever you go, and it will outlast 10 Sanden compressors. Just run it for a minute or two every couple weeks to keep the front seal oiled, and it will stay refrigerant-tight and last an extremely long time.
* I put "modern" in quotes because the axial swash plate and wobble plate designs are not new. The first such design mass produced for automotive use was the GM A5, back in 1955. That makes the axial piston design just as old as the Chrysler V2 and York and Tecumseh twin-cylinder designs. GM replaced the A5 with the A6 in the 60's, with the A6 being another axial piston swash plate design. The only thing "modern" about the current Sanden, Seltec, Denso, etc. compressors is that they are light weight and disposable. You can replace shaft seals in them, and even valve plates, gaskets, and o-rings in some models, but once they are worn out you throw them away and get a new one. I guess this makes them just like the modern vehicles they are put in. You won't see 50+ year old versions of these "modern" compressors that just need a new seal and gaskets, because they will never last that long.
I just wanted to correct a misconception: the RV2 isn't really a "power hog", it just seems that way. The amount of shaft power needed to drive a compressor depends on the compressor's displacement, volumetric efficiency, isentropic efficiency, mechanical efficiency, all else being equal. Certain other factors affect this as well, such as how much oil circulates in the system. Less oil circulation results in improved efficiency, and compressors with sumps like the RV2 circulate much less oil vs "modern"* axial piston compressors. Overall, from published results, twin-cylinder compressors like the RV2 and York are actually more efficient vs axial piston compressors like the Sanden, Seltec, Denso, GM a6, DA6, etc, and other swash and wobble plate compressors.
The reason the RV2 (and York, Tecumseh, and to some extent the GM R4) has the reputation as a "power hog" is twofold. First, they DO use a lot of power, but in return you get a very high refrigerating capacity due to their large displacement combined with high volumetric efficiency. Second, this large effective displacement combined with a relatively small, inefficient condenser results in higher head pressures, which increases power usage. Similar displacement "modern" compressors actually pump less refrigerant due to lower volumetric efficiency (VE), which means they have less capacity but also lower head pressures and thus lower power input requirements. Another thing that I think contributes to this is that the two cylinders have large torque fluctuations per revolution compared to axials with more cylinders, so when the clutch engages against head pressure the immediate response is more noticeable.
If you're not concerned with a totally accurate restoration you may want to consider safely packaging and storing your original tube and fin R-12 condenser and installing a modern (no quotes) parallel flow condenser. Sites like UAC have dimensions for OE and universal parallel flow condensers. You need to watch for the tubes and mounts to make sure a given condenser fits in the available space, and you will want to make adapter brackets to mount it without modifying/hacking your original core support. Within the constraints of your original condenser or available mounting area, you want the biggest, thickest parallel flow unit you can fit. This is true even if you use R-12, and especially true if you use R-134a. A parallel flow condenser will reduce head pressure and provide more subcooling, which will increase system capacity and efficiency while actually reducing power consumption by the compressor. A win-win-win.
All that said, you are otherwise correct: The RV2 is simple, reliable, easy to rebuild, and HEAVY! Who cares? You don't have to hand-carry it wherever you go, and it will outlast 10 Sanden compressors. Just run it for a minute or two every couple weeks to keep the front seal oiled, and it will stay refrigerant-tight and last an extremely long time.
* I put "modern" in quotes because the axial swash plate and wobble plate designs are not new. The first such design mass produced for automotive use was the GM A5, back in 1955. That makes the axial piston design just as old as the Chrysler V2 and York and Tecumseh twin-cylinder designs. GM replaced the A5 with the A6 in the 60's, with the A6 being another axial piston swash plate design. The only thing "modern" about the current Sanden, Seltec, Denso, etc. compressors is that they are light weight and disposable. You can replace shaft seals in them, and even valve plates, gaskets, and o-rings in some models, but once they are worn out you throw them away and get a new one. I guess this makes them just like the modern vehicles they are put in. You won't see 50+ year old versions of these "modern" compressors that just need a new seal and gaskets, because they will never last that long.
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Thanks, I am really struggling with getting this Duster AC to work well. I did buy a new condenser but it was a copy of the original not parallel flow and I am struggling with head pressure. I can't get all the R134A I should be able to get into it before the compressor dead heads and the clutch slips. I just found that Classic Air makes a parallel flow condenser for the '73 Dart so I am going to order one.
Jim
Wish I had been here back when you posted this. I would've saved you from a likely horrid reman. Parts for these compressors, and indeed complete NOS compressors, can be had on Ebay. Just looked today and found one NOS valve plate for the RV2, SIX! NOS RV2 compressors, and virtually every NOS part needed to rebuild an RV2. Another option is to buy relatively inexpensive "parts donor" compressors for things like valve plates, rods, crankshafts, etc. The compressor you rebuilt looked really good, and IMO you would've been better off sticking with it and just replacing the valve plate(s).
My experience with cheap Chinese TXV's has been the same as everything else that is cheap and Chinese. Again, you're better served getting a NOS valve. Another option, which I use, is to convert to a real Sporlan TXV of the type used on stationary refrigeration and AC systems. They're a bit larger and have flare inlets, outlets, and balance port connections, so either mods to the existing ends or adapter fittings must be used. However, they have massive advantages. They are more stable, have fine mesh inlet screens, are much longer lived, are made in the USA, and best of all the superheat can be adjusted while the system is charged and operating! If it's something you ever want to consider, shoot me a PM and I can show you my system with such a TXV installed. FWIW, I'm a refrigeration guy, so I kinda geek out on stuff like this
How expensive is it? Reason I ask is that universal parallel flow condensers are pretty reasonably priced and available in many sizes and configurations. Go to this link: Welcome to UAC and under "NA Types" select "Condensers". Under "NA Categories" select "Condenser". And under "NA Sub Categories" select "Parallel Flow". Then poke the [Search] button. You will get a page full of different sizes and configurations of generic non-application condensers. When you get to the bottom of the page, click the wide blue bar that says "more", and you will get more condensers. Keep doing that until you no longer get a "more" bar.
You may also want to search the application section for your vehicle and see if UAC has a parallel flow unit for your vehicle. It may well be cheaper than the Classic Air/Vintage Air tax. You can generally get any UAC parts from Rock Auto or Ebay. There's also a place here in Mesa that I deal with called Air Components that carries much of this stuff, although I have found them to be more expensive on average. Summit and Jegs have a lot of this stuff, too!
If you're patient you can also explore OE parallel flow condensers from newer vehicles that may fit your car with some mounting mods. This is what I did - I used an early GMT400 condenser (88-94 GM pickup) that is a parallel flow direct fit for the original tube and fin R-12 condenser. It was designed for R-134a retrofits in those trucks. With a few plumbing mods and bracket fabrication I was able to fit it in my square body Chevy Blazer. Even though there are parallel flow direct fit condensers for square body Chevies, thwy tend to not really be "direct fit", the cores are significantly smaller than the GMT400 unit I used, and they cost $100 more. This is just an example of how a condenser for one vehicle can be modded to fit another. What I like about the GMT400 condenser vs a generic condenser is the thickness: the universal generic condensers are typically 5/8" thick, while the GMT400 unit I used is about 7/8" thick. Every bit helps, especially with such a large displacement compressor.
I was mistaken, it is for a B body... have not found one yet. I will look at your suggestions.
Are you certain? The buyers guide in UAC's site lists it as being for a 73-74 Valiant, Duster, and Dart. Unfortunately they don't have a pic, nor do they list dimensions. That makes it impossible to determine if it's the right part, or if it could be made to work at all.
I found some tube and fin OE type replacements on Ebay. From the looks of them it would be pretty easy to modify any suitable size universal condenser to fit in place of the stock one. The universal units have fittings directly on the end tanks, and ribs on each side with holes to screw or rivet any mounts you want to them. All you would have to do is fabricate the brackets and perhaps one hard line from the looks of it. Not difficult at all, really.
Remember this Duster is a '73 Dart from the Dash forward including the radiator/radiator support/AC condenser.
Ah, I see. Unfortunately, I couldn't find one online. Call these guys: Air Components & Manufacturing Inc | Automotive Air Conditioning Parts. Ask them is they can order that part. Make sure they know it is a UAC manufactured part so they can contact their appropriate supplier. They are likely your best chance. Another place to try is Arizona Mobile Air, Inc. | Automotive Air Conditioning Parts & Equipment. As a final resort, call UAC and see if you can buy it direct, or if they can point you to a distributor that can get it for you: Welcome to UAC.
Good luck!
Max
Kaelyn and I finally installed her scoops today... She also got a 2015 CR-V with 17,000 miles on it for Christmas so we cleaned up the Duster and also finally "installed the monogramed California Cover, darling"
FINALLY the Daughters Duster will freeze your nipples off. I will try to limit my rant of aftermarket parts. The POS aftermarket expansion valves flood the evaporator and I went through 3 compressors where the super heat was totallly wrong on the valve and flooded liquid into the compressor failing the reed valves. Bought NOS reed valve plates and a NOS expansion valve (yes it is R12 BUT THAT DOES NOT MATTER). I plan to tighten the spring in the valve on turn in to compensate for the R134A with this valve but all the problems are gone and it is flipping cold 32F on the road on a 75F afternoon.
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Scamp Rhonda
Well-Known Member
32 degrees, nice!
I'm glad you paved the way for the rest of us nieve people in need of a nice AC set up. I'll be doing my original AC over in my 72 Scamp and will be looking at all your posts. Thanks much. Steve
Just rebuild your original RV-2 and buy a NOS expansion valve. If you look into the end of it there is a spring with a hex sleeve for adjustment. I am going to tighten that sleeve to put more pressure on the spring 1 turn to compensate for the R12 in the NOS valve and the R134A saturation temperature. I used a NOS front seal as well and it held a vacuum for 24 hours without dropping at ALL. Never seen that before. So bottom line all the crap about needing to "change over" to 134A is crap. I spent a lot of time learning AC and thermodynamics in the last 2 weeks and now understand it. New green o-rings on the lines and that one small adjustment of the original expansion valve is ALL you need to do. Then only fill it with about 80% of the R12 fill number.
Scamp Rhonda
Well-Known Member
Thanks again. I've book marked this and a lot of your other posts. My plan is to work on the AC after our cruising season is over here in Minnesota and make my wife happy cause she likes it cool when we're crusin. Lol
Unless the superheat is way off, I would leave the valve alone. They are adjusted from the factory for an appropriate amount of superheat, and the difference in superheat with R-134a will only be a degree or two at most. Not enough to worry about.
For the enlightenment of those who wonder about such things, Jim is correct about the NOS R-12 valve being fine to use on R-134a. If you look at, say, a Sporlan medium temp TXV power head for R-134a, you will see it is marked "R-12 R-134a R-401a". That indicates that it is intended for use with any of those refrigerants. In fact, there are about a dozen refrigerants, most of them interim blends intended to replace R-12 without having to change out the mineral oil, that will work with that power head. As long as the pressure-temperature relationship near 32°F is in the ballpark of R-12, R-134a, and R-401a, that power head will work.
Your mention about holding vacuum for 24hrs is notable. I have long been a proponent of keeping R-12 in any system that was originally R-12, especially of you want to use the original condenser. Many balk about the cost, but in the scheme of things the cost of a full charge of R-12 isn't that much extra when the cost of refurbishing the entire AC system is considered. The main thing is to make sure the system is absolutely leak-tight. With modern barrier hose, neoprene (or HNBR) o-rings, and a tight compressor, an R-12 charge should last for years before a top-up is needed. All compressor shaft seals weep a bit, but as long as the system is run for about 5 minutes every couple weeks that leakage will be very, very small. I've probably mentioned all this before, but it's worth repeating: carbon seals are excellent, reliable seals, but they must never be allowed to dry out. They rely on an extremely fine film of oil between the carbon and the lapped seat to fill in any microscopic voids and prevent leakage. Over time, the pressure in the crankcase will slowly force the oil out from between the carbon seal and the lapped seat. If the seal is allowed co completely dry out, not only will the system leak, but on the next startup the dry seal will wipe itself out and likely never seal again. At that point the only fix is to replace the seal. The only way to avoid this is to maintain the oil film by running the compressor regularly.
All of the above is also the case for a system with POE or PAG oil and R-134a. The system must be run regularly to keep the seal lubed. Otherwise, same result. You will wipe out your seal and lose your charge. The only difference is that you won't cry as much when you lose a full charge of R-134a vs losing a full charge of R-12.
This is great information. Is there anyone out there who rebuilds and repackages OEM air conditioning equipment commercially?
My original under dash stuff was cleaned and freshened when I did the rebuild on the car 6 years ago, but I have not decided what to do with proceeding under the hood with the AC. It’s the last thing left to do.....
My Coronet is all factory parts with the original Compressor restored with a new seal and Ester oil and 134A. It has worked perfectly for 5 years now with the original hoses and valve. So at 32F I take from the charts that the super heat is 5 degrees higher with the 134A not 1. I would not be concerned about 1 degree either, can you help me understand the 1 degree?
I just got the OEM numbers from the parts book and put in eBay searches. If you don’t find anything save it so it notifies you when something come available
I still have all the AC stuff for you.
From the Duster you parted out? You were going to get me a shipping cost I think.
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