I very much appreciate all of your help and patience with my AC questions. I have worked on just about every part of a car and have avoided bringing it to a shop except for tires, alignment and AC. With all of your help I feel ready to do the AC, but I'm still learning and acquiring the tools needed. I am still looking for a fridge compressor but wonder how it will hold up for 2+ hours (or overnight) if there is no refrigerant circulating through it as it is designed to do in a fridge. Doesn't the compressor need lubrication/cooling? I have not dug into a fridge yet but I would guess I will also need a/the motor to drive the compressor. Or is the compressor and motor integrated into one on more modern units?

I don't mean to beat a dead horse to death but what is the real problem with the Robinair venturi pump? Would it be one of these reasons:
1. Uses too much shop air (spec says 4.2CFM at 75psi)? My 3hp 30gal compressor is rated at 9.6cfm at 90psi. I know it's not good to run so hard but for me it'd be once in a while. Hopefully much less than once every few years.
2. Not a deep enough vacuum? The Robinair claims 29.7" Hg vacuum at sea level which is deeper than other brand venturi pumps i've looked at. LarryBible said in a post from May 2002 titled "Ac Compressor Into Vacuum Pump ?" about his now gone home made vac pump, "It pulled a very good vacuum, about 27 or 28 inches." and that was enough? Moab_dan in this post string said his freezer vac pump goes to 32Hg gauge. This would seem unlikely (impossible?) to me if 29.92" is 0 absolute at sea level (ignoring barometric fluctuations which are less than +/- .6"Hg I believe). I doubt he's a couple of miles underground either. It's impossible to go deeper than zero!
3. Your gut feelings are that venturi pumps are no good and you can't trust their spec. But an electric pump from a working fridge or freezer is good/better?

So how deep is deep enough. Can a fridge pump really go down in the double digit micron region. Somehow I really really doubt it.

Larry and Dan, please don't think i'm picking on you by quoting you. I value and learn from your advise as well as from most of the other posters. Thanks for helping me out!