I found an old cast iron 50 + year old 2 stage air compressor and I was wondering what RPM's I should run it at. My dad says it is running much slower than he remembered and it is going 323 RPM's compared to the original gear ratio that would have run at 269 RPM's. That should be dramatically faster, so could going too fast decrease performance, or something, or is there a reason the original motor may have slowed down? The RPM's are a complete guess based upon the 1725 RPM motor average. The only reason I had to change pullies was because the original had FLAT BELTS (awesome) from back when people cared and build stuff right. Now I have a v-belt on it and the compressor pulley wobbles by like 2 inches and the thing is out of line, but these shouldn't be slowing it down. Basically I need to know what RPM's I should be running the compressor at.
P.S. It can double as a vacuum pump and it uses old fashion check valves!