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I Forge Iron

Repairing/Rebuilding a Quincy compressor

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I've got a Qunicy compressor that just started making some heavy knocking noises.  I did shut it off immediately when it started making them, so I'm hoping there isn't too much damage.


I'm going to try and photo-document the process.  I've got a gasket kit, so I'm going to install that as long as I'm taking the head apart.


Here is how it looked when I got it:




This is how it looked after I put in the unloader mod so I could run it continuously when using my air hammer:




And here is the gasket kit:



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Good Morning,


Heavy knocking sounds are not repaired with ONLY a gasket set. Typically the connecting rod is splash lubricated, either it got low on oil or it decided that it needs some attention instead of just sitting in the corner.


Don't be afraid to take it apart, it is just like an lawnmower engine except with reed valves.



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I know that the gasket set will have pretty much nothing to do with the problem I've got, but I figured I might as well replace them as long as I'm going to be taking it apart.


Oil level is good, and the oil is clear.  It probably hasn't run 20 hours since the last oil change.  I don't really use it unless I'm using the power hammer.

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I have an old model #5 that was knocking when I bought it. Pulled the side cover, and the rods were toasted. They do not have bearings, and were just aluminum on iron. The oiler is a phenolic ring that slowly rolls over the crank spreading oil.  I looked into boring the rods, and fitting bearing shells after having the crank ground since this model was obsoleted in 1946 according to Quincy.  The project sat after I closed my shop, and as it turned out I found a newer model pump head on Craigslist for $60.  Still have the old head, and my repair it when I get some time to mess with it.

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Here is the top of the head from both sides:






This is the view from the air filter intake:




And this is what the oil looks like.  Nice an clean:




Well, it was easier to see the oil before it was resized.  Oh well.

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  • 2 weeks later...

Update, I got the low pressure piston out.

Before cleanup


I found the broken section of the ring, or at least part of it


I'm thinking at this point that the aluminum chunk I found was a piece gouged out of the piston face.

The oil grunge came off pretty easy, this is just after rinsing it off with solvent and a nylon brush


I included my finger for a size reference


The rest of the patina came off after some light rubbing with an ultra-fine scotchbrite pad.


And a close up again of the cause of my problems.



It took a little bit of work, but I got the bugger out!


Man, was that a deep gouge!


Well, after getting it out, I stoned the face and cut off any bit that looked like it might eventually break off.


Looks like it should work fine now without any further problems.


I also checked out the pin and connecting rod bushing, and there is only a size difference of about .0012" between the two parts. Close enough it should be quite a few more years before I need to replace it.


The ring grooves are in good shape. The maintenance guy at my work who used to rebuild Quincy compressors said they look to be in great shape, and he just recommended flipping the top 3 over to even out the wear.

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