Quincy 325 Rebuild

[Richard D]

I have a Quincy 325 compressor(1981 I believe). I bought it with no tank. I got a horizontal tank from a buddy and plan to retrofit it all together. Any pitfalls I sould look for? Its been sitting in the weather(along with the 5HP electric motor) for several years, but I can still feel compression when I turn the flywheel.

What size tank would be ideal? What CFM, PSI, etc should I expect? I read something about a hydraulic unloader, what's that?

 

[mrpizza]

It uses oil pressure (or rather the lack of it) to unload the valves until the pump has sufficient lubricating pressure to start compressing air. Basically it uses oil pressure (this is where the hydraulic part comes from) to close a valve which then Stops unloading the valves. There is a tiny hole that lets the pressure off on the side of the unloader towers. I would probably put it on a 60-80 gallon tank. Your pump, depending on motor hp and pump speed will output approximately 18.5 cfm at 900 rpm pump speed. About 9 cfm at 400 rpm. A rebuild is not too difficult but it may not need it. Pull the head and check the cylinder bores.

I know all this because I rebuilt a Quincy 310 a while back, similar style pump.

 

[mrpizza]

And to add, when you hook it up you may (probably will) find that it leaks air back through the valves when it shuts off after the cycle. These compressors typically did not use check valves from the tank, but relied on the valves to hold the pressure. The valves are little metal discs on springs that have a seat inside the valve body. Compressing air creates a lot of moisture which causes the valve discs and seats to rust. Then the disc doesn't seal fully and you get air leaking back through. Best bet is tear down the valves and lap them on some fine fine grit sandpaper to make them glass smooth, valve disc seats as well. I used 800, 1000, and then 1500 grit on mine. It is important to run the compressor with no load (meaning with your tank outlet open so air doesn't compress) for 30-45 minutes to "seat" the fresh discs and seats.

 

[Richard D]

Thanks for this advise, I am down here on the Gulf Coast so humidity/moisture is a factor.

 

[larry_g]

Quincy data

the above link has 325 specs on it. Output dpends on motor and speed driven.

lg
no neat sig line

 

[GeorgiaHybrid]

Richard,

The biggest problem you will have with that compressor is NOT using it enough. As noted, they are prone to rust in the valves over time if not used much but if run often, they will get warm enough to burn off any moisture on the seats. The good news however is that the valves are fairly easy to remove and don't require the head to be pulled.

I still like listening to my 325 quietly chug along after being at other shops with faster turning compressors.

 

[Richard D]

This will be mounted outside under cover for use in my personal garage. It's really humid down here as well. Should I bleed it down and run it weekly if it doesn't see much use?

 

[mrpizza]

Absolutely.

 

[Munchies]

PM me or email me if you need any help. Found a good parts source.

Pop the inspection covers and drop the main bearing caps. see how the babbit is looking.

Pull the oil pump/bearing carrier assembly off. Check for rust on the bearing race and the cone. Clean any sludge, watch the oil gallery/passage. Check the condition of the oil pump, and put a fresh gauge on it to see if it is making atleast 18psi.
What ROC is this pump?

 

[Trey T]

Awesome. How much did you get it for?

 

[Richard D]

Revisiting this thread as I am finally getting around to doing this compressor. It fell over on the pulley side and bent the crank. I got another used crank for it($100). The inside of the compressor looks brand new, shame I have to rebuild it. I paid $150 for the compressor, 7.5 H.P. gas motor, and 3 H.P. electric motor(an old one with cast iron housing). The tank was free. It was cracked at the leg and I repaired it. Still leaks a tiny bit, I kept welding and new leak would come up, so I'll just let it leak. Can't even hear it. My hoses leak more so it should not be a big deal.

 

[Railguy]

I just bought a quincy 325 kinda took chance on it. When I got it home and started looking at it there's at lot of part s missing off the head. You said you found a good source for parts and you got a used crank. Is that source still good?
Also I can't seam to find good diagram so I don't know what all is missing.
Any would be appreciated.
Thanks railguy