What’s an EPR valve?

It is a valve located in the rear of the v2 compressors for regulation purposes.

Check it out in the service manual. I would think the only way to know if one is there or not is to pull the hose fitting off the back of the compressor and see if it is there.

Greg

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http://www.youtube.com/hyperpack

Picture of EPR valve. https://www.ebay.com/p/1537728312
When converting to R134a it is best to remove this valve, and install a thermostic switch for clutch cycling
If you want send me a PM and I will give you my phone number. Might be easier to talk this thru.
PS: I did check, and 1974 "A" body did have an EPR valve. They were used thru 1975.

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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

I guess the question now is: "Do I have to remove the EPR valve?" I suppose I could take the car into an AC shop and have them evacuate the system to recover the refrigerant, then I could remove the valve, and recharge the system. The AC currently blows cold and ultimately that's the goal.

No, you don't have to remove the EPR valve, but the evap temp will not be as cold, due to the difference in pressure/temp relationship between R134a and R-12. If you do remove the EPR valve you need a method to prevent evap freeze up. That is done by adding a thermostatic switch in the compressor circuit, that senses the refrigerant temp at the evap outlet.

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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, it's been nearly 3 years since my last update. So here's a quick summary and update:

1. Front and rear suspension were completely (or nearly so) replaced. New ball joints, bushings, and shocks. Note that I repainted the upper control arms and I did not mask off the threads for the upper ball joint. This was a huge mistake that made installing the new ball joints a pain. And then I found out that they make a special wrench for this job. Lessons learned and all that. She rides nicely, but still very soft. I'm considering adding a front sway bar to help mitigate body roll. The alignment was bad for a while and Roma procrastinated with an alignment. As a result, the inner side of the tires are worn down to the belts. Even after a subsequent alignment, I'm not happy with it. It had a lot of negative camber until I dropped the torsion bars down a bit, but now the tires rub a bit. I think the 205/75R14 are just too tall. I'll be downsizing to a shorter sidewall next time. Additionally, most of the suspension parts were Mevotech. Almost all of the rubber boots have split. I've used Mevotech for other vehicles but this is the first time I've seen so many failures so quickly.
2. The main fusible link burnt up and took a piece of the bulkhead connector with it. I was removing the dash for some reason and I shorted the ammeter terminal. I ended up abandoning the fusible link altogether and adding 8AWG wire with a 50A (I think?) maxi fuse from the ammeter, through a grommet in the firewall, to the battery.
3. The fuel tank leaks, especially if the cap is off or has a failed gasket. We found that the cap gasket was bad on the original fuel cap, so I used some old rubber sheet I had and cut a new gasket. That only lasted a year, so a new cap was ordered. The new cap needed some filing to get it to fit, but it seems to work. If I remove the cap and the fuel tank is nearly full, fuel will leak out. It appears to be leaking around the seam, as I removed the small plate in the trunk to inspect the fill inlet tube, which appears to be fine. Given the amount of rust around the tank and what we've found in the fuel filter, I assume the tank needs a full replacement.
4. Braking performance had begun to significantly degrade. The fluid in both reservoirs in the master cylinder were rusty, even after purging them and refilling the fluid a couple of years ago. The front drum components were replaced back then, too. I don't recall if I did the rears or not, but I think I did. I confirmed that the adjusters were in the right orientation, lubricated, and appeared to index when the lever was applied. Roma didn't know about using reverse to trigger the adjusters, and she didn't like using reverse anyway, so I'll monitor the adjustment over the next couple of months. The gasket for the master cylinder cover was shot. The master cylinder sealing surface was rusty and pitted, too. So I got a new master cylinder and installed it last month. A power disc brake conversion is in the "highly desired" list, but too spendy to do right now.
5. The ignition switch died. The first and second replacement parts were bad but third time's the charm. Similarly, the turn signal switch began to act up but that was due to the connector for the wiring harness going brittle and falling apart while working on the ignition switch, dash, and speedometer. I ended up depinning the connectors and making my own connector. I'll eventually want to use a more robust connector, but it works for now.
6. The turn signals stopped flashing. With the new LED lamps, but original flasher doesn't pull enough current to trip the on/off cycling of the flasher relay. I needed to get a self-powered flasher relay, which worked fine for a year. But it failed about a month ago. If you move the turn signal arm to left or right, the lamps turn on, but won't cycle on/off. The flasher relay is behind the AC vent and under the center of the dash, and it's far too hot in OK right now, so this repair goes into the "repair when the weather is cooler" bucket.
7. She's developed a noticeable vibration when I shift into reverse. This happens even when I'm not moving, so it can't be the u-joints, driveshaft, or diff. I suspect that this is a transmission issue. I'll do a fluid change, get that tested, and see if that helps.
8. She doesn't like to idle below 1100 RPM. Or, rather, if I drop the idle down to 800 RPM (park or neutral), and then put it in gear with the AC on, its a 50/50 shot if she stalls. Vacuum at idle is good. All-in timing is around 32' BTDC, IIRC. I suspect that this is due to the cam profile. She sounds like she has a random misfire every now and then (at idle), but it doesn't sound like a lope-y cammed V8 engine. Maybe related, but at just-off-idle, the misfire seems to get worse. I suspect that this is during the phase of the throttle plate where the transition slot is doing it's thing, so maybe a carb adjustment is needed?

In other news, Roma started her first semester of college, and she's not allowed to have her car for the first year. This, plus the fact that my 2012 Ford Focus (with the dreaded DPS6 transmission) finally dies after 315k miles of service, now means that the Valiant is my new daily driver.

To Do:

• Change coolant. This is still the first fill after the descale and flush. It's turning opaque, so it's due to a DI water flush and refill.
• Fix/replace fuel tank.
• Still needs a muffler. The exhaust pipe dumps right under the driver's seat. She's a bit loud.
• Interior. The carpet is shot. The driver's side of the front and rear bench seat are torn and need repairing. I'd like to go back with some sound-deadening mats under a new carpet.
• There's a leak, likely in the windshield seal or rear glass seal, or both. When it rains, the trunk gathers water and water also drips onto my legs.
• All of the window guides are gone. The glass rattles in the channels and the wind noise is getting annoying.
• The low pressure return line for the AC has a small leak near the compressor. It gets oily after a bit and my refrigerant sniffer tells me that the bubble in the rubber section is the source of a leak. The system need a 12oz can of R-134a every year or so, which isn't too bad.
• The drum brakes don't seem to be be auto-adjusting. I've had to manually adjust the spreader wheel. Monitor for a while.
• The transmission shifter has gotten sloppy. I think a bushing or some such may have failed. In order to get it into DRIVE, I have to go to "2" then back up to "D". If I have to work on the trans for the reverse issue, I'll certainly look into the detents and such as needed.