Thread: Working on Quincy 325 - Got Some Questions

Here's a pic of a used Quincy 325 that I picked up. It's currently connected in the "dual control with shut off valve configuration":



However, I just want your typical "runs when pressure switch says the tank needs air and shuts off when the tank is pumped up" config. Is that what Quincy calls "loadless"?

Do I have all the parts I need to convert it to a simpler configuration?

You'll need a pressure switch - this is wired to the motor starter contactor coil.

Thanks for the info. I have a pressure switch already. I'm not worried too much about the electrical controls part of a new configuration yet, just the hydraulic stuff. Let me ask the question in a different way...

According to the parts book, the 325 was available in several different configurations:

"Plain"
"Loadless"
"Pilot Controlled"
"Dual Controlled Without Shutoff Valve"
"Dual Controlled With Shutoff Valve"

I've got the last version "Dual Controlled With Shutoff Valve". I'm not sure of all the details, but I've been able to glean from the parts book that the pilot controlled versions (the last three) are intended for applications where the compressor motor runs constantly and the pressure control in the tank is done with the unloaders and the pilot valve.

I don't want that. I want to simplify the system and do my pressure control with a pressure switch on the receiver. I am wondering what, if anything, in the original control plumbing needs to be changed in order to support that. I'm not sure if I've even got the right unloader valves to run that configuration.

Since almost all the threads here talk about problems caused by rusty unloader valves, I took mine off today for inspection. The lower pressure unloader looks pristine. The high pressure unloader was rusty, but I think it's salvageable.

I'm weeping oil from the seam between the cylinders and the crankcase and am torn between pulling it apart to fix the leak, or just living with it.



Looks like I could pull the cylinder assy off with the head still attached and pistons still installed by taking off the lower connecting rod caps. Don't even have to mess with the head gasket? Is it really as straightforward as it appears or are there gotcha's?

Hello? Is this thing on? I know there are some Quincy experts in the house!!

Sorry I can't help, I have a Quincy 230 that I'm going to put together.

Originally Posted by FTF Engineering

I've got the last version "Dual Controlled With Shutoff Valve".... am wondering what, if anything, in the original control plumbing needs to be changed in order to support that...

I have a dual control 308. I switched it to "loadless starting". To do that, tank pressure is connected to the oil pressure-actuated valve (aka hydraulic unloader assy) and out from there to the two intake valve unloaders. All the other crap gets removed...

Thanks Jim, That's what I figured.

a) Disconnect the current input line to the hydraulic unloader from the air line "T" and connect it directly to the receiver tank instead.

b) Disconnect the current output line from the hydraulic unloader from the "dual control check valve" and connect it directly to the unloader valves instead.

c) Take everything else off and store it in a box on a shelf.

Done, right?

Originally Posted by FTF Engineering

Looks like I could pull the cylinder assy off with the head still attached and pistons still installed?

Yeah, that works. Here's a pic of mine when I did it.

Hey FTF, Thanks for the pic. I appreciate the effort!

Your welcome.

Saw you fumbling through the work on your compressor and figured I would try to help you out. It seems you've never worked on one of these before?

Nope never. I'm not new to things like this, but I've never been inside a Quincy before.

Thanks again for the help!!

Well I'm sure no expert, but I'll be happy to help if I can.

I'm kinda surprised that one of the local experts hadn't chimed in. I know there are some people on the forum with lots of Quincy experience. Probably down to every nut and bolt.

Originally Posted by FTF Engineering

I'm kinda surprised that one of the local experts hadn't chimed in. I know there are some people on the forum with lots of Quincy experience. Probably down to every nut and bolt.

Yeah, me too! I'm beginning to think that maybe I smell or something?

Originally Posted by FTF Engineering

Yeah, me too! I'm beginning to think that maybe I smell or something?

I would like to help, but my experience is primarily with the Kellogg American pumps.

But I can't smell anything from here.

Heck, I think you have it figured out. For added assurance watch those great Youtube videos referenced in the previous 325 thread. No way somebody here can explain it as good as those videos. IIRC there is a video dedicated to the unloading system version you want. I have a 308 and a 325, great compressors.

Thanks guys.

Part of the work I'm doing to the Quincy is moving it from the original 80 gallon horizontal to a 60 gallon vertical to save space. I've got the crankcase and motor bolted to the new tank, and today I'm hoping to get the cylinder assy reinstalled. After that, I'm going to mess with the suction valves and unloaders.

Speaking of that, are the low pressure and high pressure suction valves and unloaders the same? I ask because the low pressure side is pristine, while the high pressure is rusty. I'm assuming this is because water comes out of solution after the intercooler meaning that the high pressure side will see a lot more moisture than the low pressure?

I was thinking of swapping the two just to even out the rust, but I don't know if they are the same.

Hey! FTF,

Thanks for putting this thread up and adding to it.

I've got a 390 on a 200 gallon tank, (never fails to impress the locals!).
Had that same rusty unloader prob, went with the 'run it and see what happens / lazy boy method.', a couple years on, still running better than ever, but now that you've pointed out the way....may have to do something about it...course, have to get an engine hoist into the mix to pull that sucker!

Been pretty serious about oil and filter changes, eases my guilt about the other thing.. I love all the access you get with the side panels off the crankcase on these.

Love those QR's...really makes me feel bad about all the time and money I spent on lesser compressors..

Hey Jess,

Engine hoist you say? Good timing!! I put the cylinder assy back on this afternoon using exactly that!



It was sitting on the work stands in the background and I picked it up with the hoist and lowered it down onto the crankcase which is now on top of the 60 gallon vert. I don't know what that cyl assy weighs... Some big burly machinist wouldn't even use a hoist, but my spine is already trouble. I'm not too proud to admit it's not worth the risk.

If the 390 is like the 325, you wouldn't need a hoist just for the unloaders. They're small stuff.

I have a couple 325's and when I have problems or need advice I call my local Quincy dealer and eventually get to talk to one of their mechanics who have been extremely helpful.

Originally Posted by FTF Engineering

a) Disconnect the current input line to the hydraulic unloader from the air line "T" and connect it directly to the receiver tank instead.

b) Disconnect the current output line from the hydraulic unloader from the "dual control check valve" and connect it directly to the unloader valves instead.

c) Take everything else off and store it in a box on a shelf.

Done, right?

Yep that's pretty much it. I didn't overhaul anything on my old 308. I did find that the HP exhaust valve leaked a tad, causing too much tank pressure drop overnight. I just added a check valve, like a common, run-of-the-mill compressor uses. It shouldn't be needed on a Quincy if your HP valve is in good shape, though...