Automotive Air Conditioning Information Forum

thanks tim for the recommendation. that r4 unit seems to have a small pulley. what rpm is that safe for? what hose blocks are available?

There are 2 pulley sizes for the R4 serpentine. That one is the smaller of the two. It was standard on the 5.7 & 7.4 V8's with their generous crankshaft pulley.

There is a larger pulley, but you would give up capacity at idle. Most of the 5.7's in the mid 1990's upshifted above 4800 rpm. If you plan to spin that LSX to 7500 you may want to shut the A/C compressor off.

I believe the LS crank pullies I have seen are smaller than the 1995 truck 5.7 crank pulley.

Tim should have a block for that, standard GM block. A -10 suction should be ok, yours is short. The R4 is not as sensitive to suction load, because it has no control valve or variable displacement.

bohica2xo wrote: Tim should have a block for that, standard GM block. A -10 suction should be ok, yours is short. The R4 is not as sensitive to suction load, because it has no control valve or variable displacement.

Not a lot of choices on stocked items anymore. Frankly, the best option is using a junkyard hose set and cutting the manifold off. Rebuilding the lines to fit one's needs.

Pretty sure I already provided links to the blocks we could get.

the r4 uses the same style blocks as the v7? thanks again guys. this has been very helpful.

Yep. GM kept that manifold footprint across several compressor platforms.

The R4 began to replace the A6 in 1975 for some GM cars. It was widely used for the next 20 years. I believe the 1996 Buick Roadmaster was the last production car with the R4.

Then came the parade of compressors - H6 DA6 HR6 V5 V7 And finally the shift to Nippondenso compressors.

I am sure I left some out, but there were a lot of compressor models with the same manifold pad.

UPDATE:
installed a brand new r4 style compressor using the holley bracket. no other changes.
the psi's look better and it will cycle on and off, but still only getting 20* temp change.
engine running approx 1500 rpm. max a/c in recirc posistion heater core shutoff, cooling fan running.
approx 80* ambient temp i'm at 200 psi high and cycling at around 15 psi low. evap core is frosted inlet and outlet.
plenty of air from vents only 60* temp.
any thoughts? change ot? go back to r12? aftermarket underdash unit? i'm stumped.

Your evaporator core is cold as hell. Your vent air is not going over it.

the condensor is cold and all the air is going through it. i sprayfoamed the core to the case so it's completely airtight. the way the system is, is 2 separate air ducts and vents and 1 fan. it even has 2 separate control heads for heat and a/c. i think it may need more airflow, but i'm not sure how. if it was lack of airflow, it would seem like the air would be really cold, just not enough volume to cool the car. the cycling switch seems to work. it cycles on and off at about 15 psi. is that too low?

Long thread. Has re-heating such as faulty blend doors etc been discussed. Sorry if it has been addressed

15 psi 134a is around 15f.

If your lines in & out of the evaporator are cold enough to freeze atmospheric moisture, then the core is that cold as well.

If you are blowing air over an evaporator that is that cold it will be very cold on the discharge side. Well, at least until the core freezes solid from collection of atmospheric moisture.

But since you insist that all of the system air is passing through the evaporator core, wait a few minutes. When the core ices over you should see a big reduction in airflow from the vents. Shut the system down, and watch the condensate drain.

If your problem is ice formation, re-adjust the cycling switch to close around 34 psi.