Which way to turn pump?
Pump from 1938 Scaiffe compressor
This is the pump from a compressor with a 20-gallon receiver, manufactured in 1938 by Scaiffe & Sons. I am rebuilding the compressor and have come across a question to which I seem unable to find the answer in this website; I apologize if I've simply overlooked it. (Despite its age, the system is in good condition; it has not been used for 50 years, and was stored in a dry, heated room throughout. I've already had the receiver hydrostatically tested to 200% of its service pressure.)
I need to replace the motor in the system because the original motor is (the only part that's) missing. Here's the question:
In which rotational direction should the pump turn when driven by the motor? I'm unable to determine the correct rotation by cycling the pump by hand; I seem to get compressed air out of the outlet regardless of in which direction I turn the V-belt pulley.
Which way should the motor drive the pulley as it is depicted in the photograph: clockwise, or counterclockwise?
Many thanks for your help.