Hello sorry I’m new here. And New to old school compressors. I got this compressor off my uncle worked great actual broke while I was using it at his place. I believe it’s a 80gallon tank it’s a gilbarco with a Quincy 308!head on it. Had new electric motor up on last year a 5hp. It’s runs it’s quite but now it takes forever to build pressure. It looks like it might need a head gasket but I’m not to sure like I said new to this before it was a crapsman electric 30 gallon.
Quincy 308 pressure issue
- Thread starter Rmr1499
- Start date
mattblast
Well-known member
Failure to build pressure quickly is often related to valve seals. The valves on the Quincy are easy to remove and just cleaning them up makes a big difference. You can buy new valves as well but I would recommend just take them out, clean them up and try again.
There are several threads here that show the process.
There are several threads here that show the process.
rustyjames
Well-known member
While it's running try tapping on the side of the valve housing. I had a Quincey that I had to give a few loving taps just about everyday, and it was fine for the rest of the day.
TRWham
Well-known member
There may be nothing wrong. That’s a pretty small pump on an 80 gallon tank, and the 5 hp motor is more than it needs, so it will be much slower to fill than many 5 hp compressors today. Have you timed it to see what its actual flow is?
TRWham
Well-known member
Then you probably do have something amiss if its performance has changed. It does look like an 80 gallon in the pictures. That compressor would take about 12 minutes to take an 80 gallon tank from zero to 150 psig at 900 rpm. Even longer if it’s set up to run slower.
Have you cleaned or replaced the filter? It looks like it could use some love.
Have you cleaned or replaced the filter? It looks like it could use some love.
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rustyjames
Well-known member
Yes, while its running try lightly tapping on the side, use something made of metal. If you get a change then it needs to be dissembled and repaired.
mattblast
Well-known member
Before buying any parts open up the valve covers and remove the valves.
OccupantRJ
Well-known member
Cleaning carbon off a reciprocating compressor valves is normal maintenance procedure that rarely gets done as often (if ever) as specified by the manufacturer. Do that first, test it, then move on to the head gasket. You may be able to torque the head gasket bolts a bit if it just creating spit bubbles at the gasket.
Also, with power disconnected, turn the compressor by hand through a couple of revolutions. It should sound like a bullfrog croaking from the valve flutter.
Also, with power disconnected, turn the compressor by hand through a couple of revolutions. It should sound like a bullfrog croaking from the valve flutter.
Update. Replaced head gasket cleaned the upper valve on head out. Took unloaded vale off side of pump and cleaner it all out lubbed it as per what Quincy told me to do before rebuilding it. Builds to 145lbs now but now my question is how long should a 80 gallon tank take to fill. It’s 14”pulley on pump 4.5in on motor that is a 5hp that is 3450 rpm and Quincy guy said should be around 17 cfm ??? Not to sure I just don’t wanna over do it and burn the electric motor out
MagKarl
Well-known member
Measure the current when loaded at full pressure and compare to the motor nameplate.
arkansawer
Well-known member
- Joined
- Apr 28, 2013
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- 51
before you run it too much it sounds like you are running the rpms too high. is the motor original with the compressor or new? there is a ratio.
mattblast, could you provide links to these threads? I think I need to do this on the 308 I just picked up, but I don't see an obvious way to remove them. The parts diagram I have makes it look like they're pressed on.
MacMcMacmac
Well-known member
These 308 valves are a press fit together. If you take them apart, check for fretting wear which can enlarge the valve disc guide enough that the discs can float side to side during operation and not fully seal the seat.
Thanks MacMcMacmac. Any suggestions on how to remove the valve covers and unloader tower to inspect/service the valves? I can't visualize a good way to do it right now.
MacMcMacmac
Well-known member
The valve covers unscrew just like pipe caps. I actually used pipe caps on a Quincy many years ago to fill in for some missing oem parts. The unloader tower also just unscrews. I used to use a large pipe wrench on the upper hexagonal end. They usually move without excess effort. The valves are held in place with threaded rings that are torqued into place, then the caps are installed on the upper end of the rings protruding from the head if I remember correctly. It was about 27 years ago when I last worked on one.
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Thanks MacMcMacmac. I suppose "usually" is the keyword here; I was able to get one off with an 18" breaker bar, while the other 3 required a 5 ft cheater bar. The guy I got it from said it was "slow to get to cutoff pressure." After getting a peek at the high pressure valves, I think I can see why...
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MacMcMacmac
Well-known member
Looks like the culprit. P.O. probably used motor oil as well by the look of the carbon build up.
dkmc
Well-known member
Wait......is that a compressor or a coffee maker??
Do you know the recommended oil? I have asked Quincy, but they aren't really responding to me lately.
dkmc
Well-known member
Synthetic compressor oil if you want to be nice to it. Amsoil is good. But clean out the crankcase first!
MacMcMacmac
Well-known member
Any decent compressor oil will be fine. There are probably some brands available t your nearest HF or Menards or NAPA. Barring that, a straight weight, non-detergent oil will do. Do not use multigrade engine oils.