I have a 65 Chevy truck with 350 engine. New power steering pump and new belt but it squeals really loud for 1 to 2 minutes every time I start it. Pump fluid is at cold temp level. When I put pump on I turned steering wheel one side to the other to bleed air out. Any suggestions?
What is your belt tension? Does the squeal happen after the system warms up, and you make turns requiring power assist?
I am inclined upon the information you provided to say that you have a belt undertension problem. How clean is the belt?
And answer @Paulster2's question on the belt deflection. You might push with 10 to 15# pressure when you check the deflection. If the long run is 12" your deflection should be under 1/2".
Is your belt manually tensioned, or is there a spring loaded belt tensioner?
One last thing...check your belt routing to assure that you have the belt properly sequenced over the pulleys.