I have a 73 with the VIR assembly. To convert to R134 can I use the stock VIR or should I get a VIR eliminator?
If I keep the stock VIR and I just rebuild it with new O=rings and a desecant bag?

 

Keep it, it will cool better than the alternative if all is equal

Neal

 

If you keep your VIR, it will need to be recalibrated for R-134a refrigerant. I made that conversion and just went with the substitute tubing with the pressure switch in it. That works fine IMO, and there is less to fail with it.

 

The VIR was a poor system. GM only used it for a couple of years then dumped it. VIR eliminator kits are readily available and not too difficult to install.
Check this thread, I gave the full run down of replacement on the VIR and the results afterwards:
https://www.corvetteforum.com/forums...liminator.html
Cheers, Greg

 

Thanks Greg. I find most people say the VIR can not run with R134 due to pressures and must be rebuilt and recalibrated. The VIR eliminator seems to be a solution for about the same cost.

Some writeups say you have to cut and fabricate the hoses to make the eliminator work? did you have to do this??
Thanks Jim

 

The VIR is a compensating valve (Thermostatic) that will compensate for all running conditions unlike the fixed orifice, the issue with automobiles is the compressor is a PD compressor and the engine rpm changes cause large volume changes which means that at idle when the load on the system is at its highest the compressor is at its lowest speed, not the ideal condition for cooling the interior of a vehicle with a load that can require near 2 tons of air to cool it. The fixed orifice is a compromise that will not work as good as a compensating valve at all operating conditions. The cost for maintenance when comparing the two is less for the fixed orifice but you will give up cooling capacity for savings. The adjustment that most talk about within the VIR is good for around 3* at the coil, not needed in my opinion as you will not feel that with the naked hand. If care is taken when servicing a VIR system it will cool better and give as good service as the fixed orifice system. GM switched to the VIR in 73 and made changes to it in 75 to improve fuel consumption then they were fazed out later for the fixed orifice. The fixed orifice works but is a compromise, they are used by most US OEM's today.

Either way you go when switching to r134a the best addition you can make is a new parallel flow condenser as r134a is more efficient than r12 but operates at a higher head pressure.

Neal

 

Jim, if your hoses are in good condition you do not need to replace them when installing the VIR eliminator.
Greg