Quincy 325 ROC 101 rebuild and info depository

2fpower

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Since it seems like there is not a good guide step by step guide out there to rebuild an old quincy air compressor, decided to drop my information off here. This is the first time doing one of these, so the information comes from many sites, and I welcome anyone's thoughts.

It started a couple years ago, when I finally found a great used sandblaster locally. it could blast in 20 seconds what my old harbor freight could do in 5 minutes. BUT.... What an air hog. I had a 5hp two stage eaton and a 3 horse single stage with about 100 gallons of storage, and from full pressure, could blast for about 13 minutes before pressure dropped too low to blast.

Started looking for an old Quincy, and finally found one on a local auction from a firehouse. Well- it is actually two compressors as it is a duplex. Two compressors, two motors sitting on top of a long horizontal tank.

Great videos -- two different posters that have great info....
the compressor guru https://www.youtube.com/channel/UCwC1ngf8ooZ4nqCxgiDQPlQ

and rotarycomptech https://www.youtube.com/channel/UCCdMEgfi_NvLeyrT2VEjUfg



head and valve installation

ring and cylinder install


rotary step by step....

5HP Quincy model # 325 tear down part 1 - https://www.youtube.com/watch?v=oQ_h5sXt98Y

5 HP Quincy model #325 tear down part 2 - https://www.youtube.com/watch?v=ZWt4vmGHLPo

Quincy 325 compressor repair part 3 - https://www.youtube.com/watch?v=3y7qqWVIn3Y&t=714s

Quincy 325 compressor repair #3A - https://www.youtube.com/watch?v=PUla2yhr_zk
Quincy 325 lower end repair - https://www.youtube.com/watch?v=yzoBtbmXOu0
Quincy Compressor cylinder honing piston rings installed - https://www.youtube.com/watch?v=cbtzNQnTgBk&t=700s



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great videos.
 
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2fpower

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parts... I have been very happy with parts and advice from Pacific compressors.


but their website sucks.... so I have been buying from them through their ebay store.



got their tune up kit for about $235 shipped to the door. everything for top end and rings/con bearing work.


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2fpower

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First step is to takeoff the copper line to the unloading tower, then use a big pipe wrench to unscrew the unloading tower. Under that you should find a rubber baffle and a bottlecap type of piece under the rubber baffle. In my version there’s two plastic pieces that do the unloading. The plunger on the top has a rubber O-ring that typically goes bad. looks like there was some water/oil mixture that was in this compressor side. That emulsion looking white stuff.

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In earlier years this part is made of brass, many people replace it, but mine looked in good condition still....

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same as the above, available in brass as well.

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2fpower

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Next up is to back off the locknuts that provide pressure down on the valves. For the unloading tower high side do you need a special tool which I made out of an old socket 19 mm and some flat bar. I soaked everything in penetrating lubricant before doing any work on these.

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2fpower

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So after letting the penetrating oil do it’s thing backed off the nuts took out the three bolts on top and The threaded ring on the unloading tower. And pulled out the four check valves.

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This is that center hold down stud. really dirty, so I ran the nut in all the way and wire brushed them.

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this washer is part of the unloading system. It lets off pressure after the system shuts off, so it is easier to start. The washer applies pressure on those three studs (that have springs under them) that pushes the valve open to unload the pressure.

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Here are all the valves, the high pressure in the back look worse always. Intake on the left output on the right.

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2fpower

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I cleaned the caps with wire brush in the middle and rol-lock scuff pads on the gasket surface. Speaking of those gaskets are terrible to get off but lots of time with gasket scraper and finally a wire brush. Also wire brushed the bolts.

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2fpower

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Now it’s time to take the valves apart and throw away the old springs and washer. That washer is actually the valve. And then soak them mineral spirits overnight. I use convenience store cups, as they stand up to chemicals well. Shout out to QT....

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2fpower

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Pull off the four bolts holding the intercooler on the back side, and the six headbolts and the head will pop off. Then you can remove the six bolts holding the cylinder to the bottom, and use a brass hammer to get it loose..... (take a good whack!)



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2fpower

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Next up is to remove the two Connecting Rod phones through the side access cover, I mark them with a punch first so they go on the same orientation when you reassemble.

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2fpower

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More cleaning. First spray things down with brake cleaner then come back with a wire brush for the inside and Rol-lock skuff pad for the gasket surfaces.

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I just cleaned these with a rag and some solvent. Put on a new o ring. Before we install I will coat with anti-seize.

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2fpower

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Here is a pic of the high pressure piston soaking... it looked really bad. From my research the pistons for some reason inlongate (read oval) the cylinder walls, so I checked to see how much slop there is using a gauge -- mine was pretty good. It was time to hone.

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2fpower

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To clean the high-pressure system I use a screwdriver much like a dental pain to clean the ring grooves. Recall that I soaked it overnight as well. Put the rings on per the diagram and it’s ready to go back on
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Follow instructions on the ring install. Note that all the larger rings have a dot on the side to the top of the piston.


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2fpower

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Next up was to polish The crankshaft. Found a neat YouTube video where a guy did it with a tension rope…. For this one it was pretty smooth just dirty so I used a red Scotch-Brite pad with a little WD-40 on it for lubricant. Then looped a rope around it three times and then aggressively pulled it back-and-forth which intern spun the wrap with even pressure … spinning the crankshaft a couple times as well. Also you may see that I put aluminum foil over the whole bottom to try to keep the impurities easily removable
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2fpower

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Next step is the valves, the video does a great job of showing how to lap them with 600 grit. Plan on an hour each for general cleaning with scuff pads and wire brushes. I found that Harbor freight‘s wire brush set to use with a drill was very helpful.

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2fpower

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The video links I shared to a great job of showing you how to put the valves together, pretty basic you’re using the spring that has white on it for the exhaust. And using the new washer/valves. In the meantime I put the head on noticed the long pins which are old bolts that I cut off the heads. Made it really easy to line up and keep the head gasket and place. Torque down the head to 110 pounds and bolt on the intercooler

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2fpower

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Time to drop the valves in place, torque the top plates to 50 pounds and bolts that hold down the valves to 60 pounds install the tower and you’re good to go. I did coat the gaskets with anti-seize as well as all the parts in the tower.

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