First , can someone tell me how it should operate ? Second how can I test it? I beleive that it engages constantly , but not sure what I should be looking for. I know that I know have a constant roar from the fan area , which I didn't have before.

Any help greatly appreciated !

Constsant roar sounds like the fan clutch is locked up. Try spinning the fan with your fingers, with the engine off, of course. It should spin a little. It won't free wheel, but should spin a half a turn or so. You don't want it to spin too much, or too little. If it doesn't spin at all, it is locked up, if it free wheels, that is not good either. Free wheeling, or close, means it won't lock up and move air when the RPM's are low, so no low speed cooling. Completely locked up makes the roar, hurts MPG, and either can cause the W/P to fail. How much it should spin is hard to explain, it's something that comes with experience.
You can go to a little more trouble and remove the clutch, put the nuts back on and test drive it. If the roar is gone, you have your answer, but it sounds like it's a goner.

As far as how it should operate... In most American cars, the clutch is RPM sensitive. It's locked up at low RPM so air will flow through the radiator at stop and low speed operation. When you reach road speeds, it should unlock, as the movement of the vehicle provides enough air flow for cooling purposes. By free wheeling at road speed, it reduces the load on the engine, promoting better economy, and also, most importantly, eliminates the roar.
A lot of foreign car clutches have a heat sensitive silicone grease in the center, and it will disengage at a certain temperture.

depends if its a thermal clutch, does it have a coil on the radiator side?

It is a thermo clutch and does have a coil.

The thermo clutch is supposed to lock up if the temp goes up so the air movement is maximized. Here in Texas with A/C on you'll hear the roar after sitting at a stoplight but it goes away once you get moving. It should definitely not be roaring all the time.

David-
Good functioning replacements are available at any good auto parts store, so if in doubt, it is a minor job and not much expense to replace it.

My main word of caution is to NOT get the economy clutch without the coil spring on the front face. It is not adequate. Get the more expensive OEM equivalent one with the coil spring.

On my '63 the clutch was not locking up properly when hot. With the new clutch and hot engine, it really roars.

One common manufacturer and part number for this clutch is "Imperial" and is their part # 215049. I'm sure there are others.

When the engine is cold the fan should turn with very little resistance. With the engine hot it will take noticably more effort to turn it.
Usually the bi-metal coil type that you have fail in the opposite where they never totally get up to engine speed.
As mentioned, a replacement hub can be found at auto parts stores.
Yes it does take experience to sense the proper resistance when testing.
impala