Power steering?

[tmad]

Hey guys Ive got a question about my power steering, Its probably been asked a million times but with no search who knows! Here goes: Ive got a 67 lwb 2wd 1/2 ton w/ 283 it has factory power steering and a newly rebuilt control valve the problem is it still seems hard to turn and it does not recenter very well. I have bled and bled the system and with the front end up it seems to have a little chatter in it if you watch the tire turn but there is no whine in the system when I drop the front end I do get a small whine when I turn the wheel. I am running 235/60 rubber and Im wondering if that is my problem and if so is there a fix? any help or input would be a great help Thanks