HH56 wrote:
Packard did not as a rule provide much in detailed pressure specs and when they did it was often in a fairly wide range. On page 4 and 5 of the Power Steering Training Manual they give a bit of info on how the pump and valve operates but for specs, info is probably the same as the service manual and just says the pressure depends on how much resistance is felt at the wheels and relief valve will work if pressure exceeds 650 psi.

55-6 models used a similar design pump but had two different steering systems so pumps had different relief valves. On those the range as given in the April 55 Service Counselor is 550-800 for pumps used with Bendix systems and 650-900 for Monroe systems.