I decided to fix the few issues with my steering in my 76. I had some play in the Steering and no return to center after turns and Steering was tight so the power assist was working. First check I did was the Steering gear box, when I turned the wheel the pitman arm moved so no delay or slop. With the car running and off the ground you can see the play was in the control valve. I replaced the control valve, all four hoses and rebuilt the power piston. That fixed the play issue but had no change on the power steering, still was tight and no return to center. Yes I did the proper adjustment on centering the piston. One issue is resolved so I went on to replacing the power steering pump. Still no difference in power steering. I decided to replace the steering gear box and problem still remains. Any ideas on next steps? Could the power piston be bad causing no power steering? The car has been like this since I owned it about 5 years now. There are no leaks and I did replace all ball joints, upper and lower control arm bushings. Had the alignment done and car goes straight when driving. I did check for binding when I had the control valve out and power steering gear box out and I was able to move tires by hand from stop to stop.

I did buy the gear box and pump from Wilcox.
I bought the control valve from a local Corvette shop and I never had a issue with them before.

 

the no return on steering could be the caster angle in the alignment
on the power steering disconnect the piston from the bracket and see if it moves when you turn the wheel with the engine running

 

So I just recently did similar to my 69 minus the steering box which was still in fairly good shape for it's age. Maybe I'm missing something but you say in that first statement that power assist was working. Then in the second you say it's not. In regards to the power piston if it's not leaking then the only issue I think would be an internal flow issue. When you calibrated the valve for center the piston should have moved in and out least letting you know that it is working somewhat. Still might not have enough flow to give you enough assist not sure how to check that or the specs off the top of my head. Also I'm sure you didn't do this, but make sure the hoses from piston to valve are not connected backwards. I think that would definitely cause it to feel like you were fighting something while turning. Anyways clarify whether you have no assist, weak, or it was working and now it's not and maybe someone else will chime in. Since the condition didn't change much when you changed the pump I don't think it's there.

-CJ

 

Sorry miss stated I have no or little assist. I did check the hoses and they are crossed so top hose from control valve goes to bottom port on piston. When I centered the the piston it did move in and out but not sure like you said if that is good enough. I will try and disconnect piston and turn wheel to see if it moves.