The phone call usually starts the same way. "I need a filter for my Quincy." Then it goes quiet while somebody walks out to the machine, and what comes back is a horsepower rating, a guess at the age, and a part number that was written on the old filter in marker by whoever changed it last.
We can usually work with that. But if you want Quincy air compressor parts that fit the first time, there are three numbers that matter, and one of them trips up almost everybody.
Find the nameplate before you look up anything
Quincy builds across a lot of model families, and several of them share part numbers in some places and absolutely do not in others. Guessing from horsepower is how you end up with a gasket set that is close but not right.
Where to look depends on what you have:
- QR-25 reciprocating: the model and serial tag sits on the handhole plate side of the crankcase. On some builds, the bare compressor serial decal is on the bearing carrier, opposite the flywheel.
- QT and QP reciprocating: nameplate on the pump or on the tank near the control panel, and usually a second tag on the motor.
- Rotary screws (QGS, QGD, QGV, QSI, QST, QSB): inside the cabinet door or on the frame rail, plus the airend has its own serial that is not the same number.
Write down all of it. Photograph the tag with your phone. It takes thirty seconds and it saves a return shipment.
The third number nobody records: the record of change
Here is the one that causes the most wrong-part orders on reciprocating Quincys. QR-25 parts manuals are published against a record of change number, and the same model (say a 325) can have several of them across its production life. Parts changed between those revisions. A valve assembly or a bearing carrier that fits a Model 325 at one record of change may not fit another.
So for a reciprocating unit you want three things, not two:
- Model number (216, 310, 325, 340, 350, and so on)
- Serial number
- Record of change number
If the record of change is not legible, the serial number lets a distributor pin down the build date and work back to it. If neither is readable, the fallback is measuring: bore, stroke, and the bolt pattern on whatever you are replacing.
Which family do you actually have?
Quincy's lineup is wider than most people realize, and knowing where yours sits narrows the parts search immediately.
| Family | Type | Rough range | What you tend to buy for it |
|---|---|---|---|
| QR-25 | Pressure lubricated reciprocating, 100 percent duty | 1 to 25 hp | Valve assemblies, rings, gaskets, oil pump parts, unloaders |
| QT | Splash lubricated reciprocating | 5 to 15 hp | Valve plates, rings, intake filters, check valves, pressure switches |
| QP | Pressure lubricated reciprocating, higher pressure duty | 175 psi class | Valves, gaskets, oil system parts |
| QGS | Belt-driven rotary screw | 5 hp and up | Separator elements, oil filters, intake elements, belts, coolant |
| QGD | Fixed speed gear-driven rotary screw | 15 to 60 hp | Separators, filters, coupling elements, controller parts |
| QGV | Variable speed rotary screw | 20 to 200 hp | Separators, filters, drive and sensor components |
| QSI, QST, QSB | Larger direct-drive rotary screw | Up to the 350 hp class | Separators, oil and air filters, valve kits, airend service |
The practical split: if it is reciprocating, your parts conversation is about valves, rings, and gaskets, and the record of change matters. If it is a rotary screw, your parts conversation is about the three elements and the coolant, and the airend serial matters.
The parts people reorder most
Air/oil separator element. On any lubricated rotary screw this is the single most consequential element in the machine. A separator past its life pushes oil downstream into your filters, your dryer, and eventually your tools. The symptom is oil carryover, and it looks exactly like a dozen other problems, which is why it goes undiagnosed for months. We walked through the whole diagnostic path in blowing oil into the lines.
Oil filter. Cheap, frequent, and the one people stretch. Quincy publishes change intervals by hours and by coolant type, and running a mineral-oil interval on a synthetic fill, or the reverse, is how bearings get short.
Intake filter element. On a rotary screw it protects the airend. On a reciprocating unit it protects the valves. Either way it is the cheapest part on the machine and the one with the highest consequence per dollar.
Valve assemblies on reciprocating units. If your QR-25 or QT is losing capacity, running hot, or building pressure slowly, suspect valves before you suspect the pump. They are a wear item, and they are rebuildable on some models and replace-only on others.
Coolant. Quincy publishes specific fluids per family, and the interval depends on which you run. Mixing fluid types is a real way to varnish an airend. Our compressor oil guide covers the types.
We stock Quincy parts and compressors across the reciprocating and rotary screw lines, including oil filters and elements, along with service kits that bundle the filters, separator, and gaskets for a scheduled interval so you are not ordering four line items separately.
OEM or aftermarket?
Straight answer: it depends on the part, not on a principle.
Parts where aftermarket is usually fine, assuming a reputable manufacturer and matched specifications: oil filters, intake filter elements, belts, O-rings, standard gaskets, pressure gauges. These are commodity items built to published specs, and a quality aftermarket element from a known filter manufacturer is frequently the same media.
Parts where we lean OEM: separator elements on high-hour machines, valve assemblies, anything with a controller or sensor interface, and anything inside the airend. A separator is not just a filter, it is a specific media and a specific grounding path, and a cheap one can cost you an airend. Controller components are rarely worth the gamble.
We went deeper on this tradeoff in OEM vs aftermarket compressor parts.
Cross-referencing without getting burned
Cross-reference tables are useful, and they are not gospel. A few rules that keep you out of trouble:
- Match the spec, not just the number. For a filter, that means micron rating, flow, port size, bypass setting, and gasket diameter. Two filters with the same thread can have very different media.
- Measure the old part before you throw it away. Overall length, outside diameter, gasket ID and OD, and thread. Those four numbers settle most disputes.
- Watch for supersessions. Quincy, like every OEM, retires numbers and replaces them. A number that returns no results is often superseded rather than discontinued.
- Do not cross-reference separators by dimension alone. Media, burst rating, and static dissipation matter, and they are not visible.
What to have on the shelf
If the compressor is the reason your shop runs, a small shelf stock beats overnight freight every time. For a single rotary screw, that is one spare separator, two oil filters, one intake element, and a pail of the correct coolant. For a reciprocating unit, a valve set, a gasket kit, an intake element, and a spare pressure switch and check valve, since those two fail more often than the pump does.
Beyond that, keep the manual. Not a PDF somebody bookmarked on a laptop that left with an employee: a printed parts book in the compressor room with the model, serial, and record of change written on the cover in marker. Every parts call gets twenty minutes shorter.
Frequently Asked Questions
Where is the model and serial number on a Quincy QR-25?
On the handhole plate side of the crankcase. Some builds also carry a bare compressor serial decal on the bearing carrier, opposite the flywheel side. Record both, along with the record of change number, before you order.
What is a record of change number and why does it matter?
It identifies which revision of a given model you have. Quincy publishes reciprocating parts manuals against it, and parts can differ between revisions of the same model number. Ordering by model alone is the most common cause of a wrong part.
Can I use a generic separator element in a Quincy rotary screw?
You can, but we would not on a machine you depend on. Separators have specific media, burst ratings, and a static dissipation path. A mismatched element shows up as oil carryover or, worse, as a static-related failure inside the receiver. Oil and intake filters are a much safer place to use aftermarket.
How do I know which coolant my Quincy takes?
Check the decal on the machine and the manual for your family, since the specified fluid differs by model and by whether the unit was filled with mineral or synthetic. Do not mix types. If you are switching, flush rather than top off.
My Quincy is from the 1980s. Can I still get parts?
Usually yes, especially for the QR-25, which has been in production in various forms since 1939 and has deep aftermarket support. Older rotary screws can be harder. Start with the serial number, which pins down the build, and expect some numbers to have been superseded.
Most wrong-part orders come down to the same thing: somebody ordered off horsepower and a guess instead of off the tag. Get the model, the serial, and the record of change written down once, keep it with the machine, and ordering Quincy air compressor parts turns into a two minute job instead of a two day one.
