How do I know if the evaporator core and POV valve is any good?

If it don't work, it ain't no good...
(sorry...that was too easy...)

The evaporator core can be checked for leaks at most radiator repair shops.
The POA valve is another issue. They are rebuildable, tho, so that's good.
If the system is fully charged, but not cooling, you would need to look at the pressures on the high and low sides of the system to see if there is a restriction(too high pressure on the high side and too low on the low side [POA valve stuck closed, or some other restriction in the lines, etc.]), or if the pressures were low on both sides(failing compressor, or stuck open POA valve).

Thanks Adam. My problem is I took the evaprator box out of the car and I was hoping that I could do some test to see if the parts are working.

Well, there's really nothing to "work" as far as th evaporator itself...it's just a little radiator, for all practical purposes. It can be leak-checked...that's about it.
I can't think of any "test" for checking a POA valve out of the system. They operate off of temperature, and pressure...
I suppose if there is any question about it working or not, you could just rebuild it, or have someone do it for you...or buy a rebuilt...I'm going to have to rebuild mine for the '74...when I get the time. Not gonna happen before Hot Springs, tho...

Isn't there anything you don't know bro Joel. I'll give ya 100 bucks to move here ta my little town.

Wait a darn minute....sorry ossw1, I just jumped your thread. Gee, I guess i'm gettin too old to think of my own.

If it's actually spitting out the lubricant from the front of the compressor, it's gonna be more than just a seal.
Now...ALL of the A6(long/skinny) and R4(short/stubby) compressors "seep" a little out of the front seal of the compressor. The "seal" is actually a ceramic piece...not exactly the best thing you could use for a seal, but that's what works in that location. If yours is putting out liquid, when you run the A/C, that's a whole nuther problem...It may have broken the ceramic seal, or there may be other problems there. Did the system still have pressure when you took it apart?

[QUOTE=Adams' Apple]If it's actually spitting out the lubricant from the front of the compressor, it's gonna be more than just a seal.
Now...ALL of the A6(long/skinny) and R4(short/stubby) compressors "seep" a little out of the front seal of the compressor. The "seal" is actually a ceramic piece...not exactly the best thing you could use for a seal, but that's what works in that location. If yours is putting out liquid, when you run the A/C, that's a whole nuther problem...It may have broken the ceramic seal, or there may be other problems there. Did the system still have pressure when you took it apart?
[/QUOTE]

All we can get, Terry....all we can get....
To be honest, I don't even know. It's now where near as outrageous as R12, of course, but it's still higher than it was 2 years ago....I'll check and see what the going rape is around here...