86 Grand National

[Turbo]

Working on a Grand National ac system which has been modified. Owner wants the system to work at peek performance especially at idle. Not positive what refrigerant is in there now but it is one of the r-12 alternatives I was told, also the mineral oil was not changed. Currently it can put 40 degree temp out the vents on high blower and cycle while on the freeway on a 95 degree day but once the car stops moving vent temps climb fast to high 50's making it uncomfortable . There is a dual puller electric fan setup installed. These cars produce an insane amount of heat under the hood due to the turbos location, intercooler and piping. Other current modifications I noticed is a upgraded condenser from the factory tube and fin to a parallel flow. The r4 compressor pulley has a smaller pulley from a truck. The diameter is 4.2", can someone let me know what factory was. Also told the orifice tube is either a blue or red currently, most likely a blue.
3.25 lbs of r-12 will be going in the vehicle. As for the other modifications, would you change anything? The upgraded condenser definitely can't hurt in my opinion but the smaller pulley on the compressor and orifice tube has me thinking. What would you do? The pulley can be changed after the fill so that is not a main concern now. Would you put a blue tube in there? Many manufacturers used blue with factory r12 fills while gm went with white.
If you have any experience or knowledge which can point me in the right direction it will be very appreciated. Ty

[Tim]

130mm PULLEY DIA
28.7mm GL

SPADE @ 12

[tbirdtbird]

"Owner wants the system to work at peek performance especially at idle."
This is an impossible task. At idle the comp is doing nearly 0 work.

[Turbo]

Thank you Tim for the specs. Going to leave the smaller one in for now since changing it does not require a recovery. Also, the parallel flow should keep the pressure under control with the extra capacity at idle. Going to calculate if it will over Rev the compressor.
Tbird he would like the system to cool as best it can. We all understand peek performance can't happen at idle.

[tbirdtbird]

"Tbird he would like the system to cool as best it can"

So wouldn't everyone

You could size the pulleys so as to achieve the spec 1800 rpm at idle, but what happens when he puts his foot in it.

The traditional pulley sizes are geared for typical usage, such as stopping for red lights and stop signs.
I had to modify the pulleys on a vintage Studebaker I installed AC...I maintained the size on the comp (they are all about the same anyway), and I changed out the crank pulley from 6" to 8". I actually had to make the pulley myself. I had no more room to go.....still had poor cooling at idle, but decent cooling at speed. Remember old school (40s-50s) cars were typically 6 cyl and they idled very low and had a relatively low RPM at road speed.

[Carguychris85]

"Owner wants the system to work at peek performance especially at idle."
This is an impossible task. At idle the comp is doing nearly 0 work.

I would not say that it is an impossible task. The compressor is only doing nearly zero work if you are running a Sanden. GM V7 would be my choice as they are usually a very easy retrofit from a R4. My 1987 G20 van that is a retrofit, custom system setup because it has a L31 350 Vortec and brackets swapped into it performs fantastically even at idle. When it still had the 305 TBI and factory R4 brackets, I adapted and ran a S10 V7 on it with the lowest pressure control valve that worked very well in an otherwise stock system. Used a Ford red orifice tube on it.. With a fresh system, new evaporator core, resealed HVAC case underhood, massive parallel flow condenser and pusher electric fan it works even better now. This was using outside air. In recirculate it will reach low 30s/high 20s before the cycling switch calls it quits to prevent freezing up the evaporator core. It will hold low 40s at idle with recirculate and an interior that has cooled off. I have a Denso 10S20F 10 cylinder compressor with the factory 1.88 drive ratio (8" crank/4.25" compressor pulleys, cammed L31 idles 725 rpm with ac on), a large parallel flow condenser with a pusher fan, and this time around I used a standard GM White orifice tube as a baseline.

https://youtu.be/8UuKKrHdz9A?si=xQGo6sgSiOuFlnrj

[Carguychris85]

Working on a Grand National ac system which has been modified. Owner wants the system to work at peek performance especially at idle. Not positive what refrigerant is in there now but it is one of the r-12 alternatives I was told, also the mineral oil was not changed. Currently it can put 40 degree temp out the vents on high blower and cycle while on the freeway on a 95 degree day but once the car stops moving vent temps climb fast to high 50's making it uncomfortable . There is a dual puller electric fan setup installed. These cars produce an insane amount of heat under the hood due to the turbos location, intercooler and piping. Other current modifications I noticed is a upgraded condenser from the factory tube and fin to a parallel flow. The r4 compressor pulley has a smaller pulley from a truck. The diameter is 4.2", can someone let me know what factory was. Also told the orifice tube is either a blue or red currently, most likely a blue.
3.25 lbs of r-12 will be going in the vehicle. As for the other modifications, would you change anything? The upgraded condenser definitely can't hurt in my opinion but the smaller pulley on the compressor and orifice tube has me thinking. What would you do? The pulley can be changed after the fill so that is not a main concern now. Would you put a blue tube in there? Many manufacturers used blue with factory r12 fills while gm went with white.
If you have any experience or knowledge which can point me in the right direction it will be very appreciated. Ty

I would retrofit it to a V7 compressor for a ~2002 2.2L S10 with the lowest pressure control valve, install the largest parallel flow condenser that will fit and go back to clutch fan if it were me. Then add the largest pusher fan or two that will fit up front with whatever intercooler is up there. R134a with a Ford Red orifice tube. I have done enough R4 to V5 or V7 swaps now I go for the lowest pressure control valve and have yet to see one actually freeze the evaporator core. My first R4 to V5 swap was my 1988 Fleetwood with the underpowered Vin 9 307 HO. The V5 made the ac work far better and the V5 did not sap nearly as much power off that gutless 307 at highway speeds. I swear that car slowed down 5 mph when the R4 cycled on and sped up 5 mph when it cycled off with steady pedal at 70 mph.