I acquired this old compressor about five years ago. Finally got tired of moving it and tripping over it. Decided to rig it up (don't look too closely!) to see if it was worth saving. Originally I was going to restore it and put into service in my hobby shop, but then the place we bought came with a compressor.

It did not come with a motor so, I was thinking of putting a five horse motor on it originally. But I have a 2 hp Dayton motor with a QD twin pulley already. Myself, I said, good enough to see if it works enough to go further. Adapted that to it for testing it out. It must have sat outside some time before I owned it as the pressure switch and a couple other things are rusty. Got some new belts, rigged up some power and turned it on. Runs quiet. Builds pressure. I replaced the pressure gauge that was broken. As I suspected the pressure switch did not open so it needs that. The switch was rated for 100psi off/80psi on. Also tried to lower the cut out/in pressure but it still did not cycle. I let it build to 110psi before killing the power as it does not have a pressure relief valve (yet). The 2hp motor turns it effortlessly and it even restarts it at working load. I'm impressed as I really expected the 2hp to bog on restart.
Here is where I'm confused. When the motor is de-energized, what I think is the unloader system vents continuously. I have opened the end of the compressor facing the above photo. I can find no information about the company, M&E, nor much information about the unloader system. I think it is a mechanical centrifugal switch. When the compressor is turning it throws out and a pin on the unloader extends and shuts off the air flow. I tested this on the bench with compressed air and it seems to work correctly. In fact, if I power the motor up the air flow stops immediately. This is the unloader vent on the bottom of the round section.

Now I am lost in the weeds. There are two 1/4"OD lines coming off the head to this contraption. Should one of those have a check valve? I see nothing externally. Would a check valve be part of the head internally? Or am I not even in the right forest, let alone barking up the wrong tree? Anybody familiar with these systems? Modern compressors seem to have taken a different approach to the unloading valve so info seems scarce. If anyone knows more about this system and can make a guess as to the age of this beast I'm all ears.

At this point the unit seems worth resurrecting. Runs cool and smooth. Low power needs. No leaks evident at this time. And yes, Safety Sam, I do have the belt guard, just not installed while I test things. Yes, wiring will be done properly. I don't want to invest more until it shows that it can be saved. Thanks for reading and I'm looking forward to your feedback.


It did not come with a motor so, I was thinking of putting a five horse motor on it originally. But I have a 2 hp Dayton motor with a QD twin pulley already. Myself, I said, good enough to see if it works enough to go further. Adapted that to it for testing it out. It must have sat outside some time before I owned it as the pressure switch and a couple other things are rusty. Got some new belts, rigged up some power and turned it on. Runs quiet. Builds pressure. I replaced the pressure gauge that was broken. As I suspected the pressure switch did not open so it needs that. The switch was rated for 100psi off/80psi on. Also tried to lower the cut out/in pressure but it still did not cycle. I let it build to 110psi before killing the power as it does not have a pressure relief valve (yet). The 2hp motor turns it effortlessly and it even restarts it at working load. I'm impressed as I really expected the 2hp to bog on restart.
Here is where I'm confused. When the motor is de-energized, what I think is the unloader system vents continuously. I have opened the end of the compressor facing the above photo. I can find no information about the company, M&E, nor much information about the unloader system. I think it is a mechanical centrifugal switch. When the compressor is turning it throws out and a pin on the unloader extends and shuts off the air flow. I tested this on the bench with compressed air and it seems to work correctly. In fact, if I power the motor up the air flow stops immediately. This is the unloader vent on the bottom of the round section.

Now I am lost in the weeds. There are two 1/4"OD lines coming off the head to this contraption. Should one of those have a check valve? I see nothing externally. Would a check valve be part of the head internally? Or am I not even in the right forest, let alone barking up the wrong tree? Anybody familiar with these systems? Modern compressors seem to have taken a different approach to the unloading valve so info seems scarce. If anyone knows more about this system and can make a guess as to the age of this beast I'm all ears.

At this point the unit seems worth resurrecting. Runs cool and smooth. Low power needs. No leaks evident at this time. And yes, Safety Sam, I do have the belt guard, just not installed while I test things. Yes, wiring will be done properly. I don't want to invest more until it shows that it can be saved. Thanks for reading and I'm looking forward to your feedback.


