compressor questions

[BIGglaSS]

It is in fact a centrifugal unloader. On the other side of that cover, there are fly weights on the end of the crank shaft. As the crank builds speed, the fly weights close a ball/spring valve. Until the valve is closed, air is exhausted out the nipple in the front. The top of that should be piped to a tee on the high pressure exhaust. If it has a crank case vent, it will be piped to a tee on the air filter intake.

Off hand, I don't recognize this pump. But it looks similar to the old Kellogg's.

There are other types of unloaders that can be used to keep the motor running and the pump turning. Such as gas compressors, or even electric ones. This helps save to motor from constant start/stop cycles.

BTW, that is an excellent purchase! The motor alone is worth more than you paid. Those pumps are so simple, and can easily be rebuilt. And, QUIET!