Putting a larger pully on the motor will speed up the compressor. Think of the circumprance of the pullys. To get one revolution of the compressor, you need the circumprance of the motor pully to travel the same distance.
Check your owners manual to sure you are using the correct RPM motor, and the maximum speed you can run the compressor.
If you can run the compressor faster, you will probably need a larger HP motor.
Calender is Great! Got two, one for me and I think I'll take the second by the local CaseIH dealer so they can see what real Case tractors look like!