question, on the 80 vette I have everything loose on the control valve. The valve will twist but wont come off. I even took the bolt off that holds it to the control arm. 

I used a pickle fork to get the valve off the control arm stud

The valve fastens with a taper fit in the middle, and screws onto the other end.  Use a pickle fork as Al said to get the taper fit off, then take out the cross bolt and unscrew the valve from the relay rod.  It does not usually unscrew easily, but it will come off.

Larry