Jay,
I had a 69 camaro with a 250 p/s pump leaked had it rebuilt it whined. Brought it back the rebiulder exchanged it for another, it whined. Moral of the story, needed a new belt.
New belt due to arrive soon. Needs one anyway 'cause this one is old. I did apply a little extra pressure to the PS belt while it was running by pushing a wheel against it by hand. No change in the whine. I'll do some more diagnostic work tomorrow.
