Automotive Air Conditioning Information Forum

hi
Looking for a setup I am building at the moment SBchevy with carby and a street style cam .
Anyways the prediction is the engine wont like the a/con compressor load without an idle up or a cutout . If I remember correctly back in the 80`s,,90`s there were Sanden idle cut outs .
Carb is a Holley /Quickfuel
Have considered the AC Delco solenoid but it requires u to flick the throttle for engagement . Not that great . Originally Its an anti dieseling solenoid for the throttle. Turns off throttle when ignition is turned off .

I would be happy with either cutout or idle up . Can anyone help ???

Not sure what you mean by a cutout.
However, we have retrofitted AC to several vintage vehicles here, and always end up using a so-called fast idle solenoid. As you know, it will kick the idle up about 200 RPM or so to prevent stalling at lights. Yes, when you first turn the AC on, you will have to goose the gas a bit to allow the solenoid room to work. However, you only have to do that once when you first start it. At that point you will most likely need the AC for the rest of your drive, and the solenoid will stay activated as long as the compressor clutch is on. Of course, in the off season, the solenoid is not activated at all. Today's computer controlled cars do not need this.

Also, be sure your front crank pulley is as close to 8" as you can get. The minimum suggested diameter per ice-n-tropics' book is 7.5".
This ensures that you have enough RPM to properly run the comp. For one of our retrofits we had to fab up a larger pulley from 6" to 8"

We tried to find another solution, but could not. The method described above is quickly learned and just not an issue for us.
If you determine an alternative solution, please post it.

The Sanden

The Sanden cut out was only for wide open throttle clutch cut out for acceleration enhancement.
I rigged a WOT switch on my 59 Impala (when I was a kid w/ MARK IV building ACs for my cars out of trash cans) using a microswitch and distributor advance pneumatic diaphragm solenoid on a mounting plate with vacuum hose connected to intake manifold.
But you may need an idle rpm increase too.
REF 8" C/S pulley: Each case is different. The C/S pulley, clutch diameter, comp max rpm and displacement are all interactive and can rule out a big 8" pulley. Also, the expense of providing a big CS pulley is often prohibitive.
hotrodac

We have vintage long stroke engines here that only rev to about 3K without grenading. The 8" pulley was a necessity to get the comp revs up to a workable RPM. I think your book states 7.5

ICE, BTW, your hotrodac book is excellent, learned a lot from it!

hi
Cutout = compressor cut out , at idle in this case. Might try a carburettor linkage micro switch at idle to turn off compressor .

Delco solenoid not a good solution
Crank pulleys 5.5 inch 6.25 inch or 7 inch stock / 5.5 drag only / trying 6.25

OK, just recall that on a modern car, the compressor will underperform if the shaft speed doesn't get to 1500-1800 RPM. This is why you get little cooling at a stop light.
Today's engines are short stroke and turn faster than yesteryear. Measure the pulley diameters on a modern car. The comp pulley is usually 5 or 6 " diam

The 61 Catalina that I was air conditioning had a 7.25" C/s pulley on a noninterference engine, so I was using it as an example of how to calculate the inputs so that the max comp rpm rating is not exceeded.
My 2 cents for specifically for T bird:
Since you are fabbing pulleys (as I have given examples earlier) you earned First Prize.
I have recovered from Covid Pneumonia, but my younger brother passed.
Nothing is coincidental, even on the net.
Hope to see you up yonder if you can sincerely put your name into John 3:16, e.g.,
For God so loved Norman that he gave his only begotten Son (Jesus), that when Norman believes in Him, Norman shall not perish (in Hell) but Norman shall have everlasting life (up yonder).
hotrodac on Palestine Texas farm

I'm very sorry for your loss, Ice. Very sorry indeed.
Was in Palestine a few weeks ago, very pretty. Was there as part of a Model A club tour. Closer to Dallas is my usual haunt.
Again your book is awesome. For example that was how I learned not to block the fourth vent opening on the evap....joined 2 with a wye, much better air..