Anyone know how to convert dead A/C compressors to a useful item like an air pump? Lots of unused compressors draining horsepower and becoming dead weight that could be utilized on the older 4 wheelers, or any vehicle for that matter.

Not sure how long it would live because they are lubed for crankcase and on top end from oil in freon/coolant. They would need some for of oil injection in intake air to lube top end of compressor but they would yeild oil in output air too which may not be desirable.  

Get yourself an old York compressor off an early Ford.  They are oiled through the crankcase not the freon side so they'll hold up for a long time.  Put an air breather on the low side, and hook the high side to a small air tank.  Hook the electric clutch to a manual switch and a pressure limit switch in a series so you won't blow the tank.  

This it true but they are getting hard to find in working order.  

As you consider yourself a mine of information, what is the problem with adapting a small bare compressor to fit onto an engine bracket? Obviously it would have to be about the size of an alternator or a/c pump.fficeffice" />>>

For a bigger compressor, you could fit a P.T.O. on to the back of the gearbox. Can you still get P.T.O.'s for American 4X4's? I know you can for Land-Rovers, (if you've got the right gearbox).>>

Chevbeater was right about the old York compressors.  I have one on my Scout and am thinking about converting it.  York compressors are oil bath compressors unlike most others that use the freon like snowman said.  People I know that have done the conversion say to put a little oil into the intake side every now and then.  Keep a good breather filter on it and use some kind of pressure regulator in between the pump and the tank.  I've seen lots of folks use front tube bumpers as tanks, or use a small fire extinguisher bottle for a small tank.  Good luck!

Scoutnut