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Please look at the compressor photos I have a few questions

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by Rob
(Hartlepool, United Kingdom)

Hello all, would you be so kind as to look at the photographs of this old compressor and help me with a few questions I have regarding it.

I have owned this compressor for a long, long time, and in that time have changed the motor perhaps two or three times, the original bit the dust many years ago, and some of the ancillaries are now different, which can be seen from the photos.

Compressor Front Id Plate
Compressor Front Id Plate
Compressor front view
Compressor front view
Compressor pump head showing hole
Compressor pump head showing hole
Overhead View Of Hole Top Groove Of Pump
Overhead View Of Hole Top Groove Of Pump

The removal men when I moved house managed to drop it on its side smashing the original pipe and guage oh so many years ago Manufactured in 1958, just eight years younger than than me lol it still runs today and is a good compressor however some things have always intrigued and puzzled me about it. Does anyone know the answer to the following questions:

The pump has always had a part missing, well since I got it second hand,this fit into the hole in the centre groove and can be seen in the picture,interestingly though there seems to be no thread in that hole to indicate what was placed there originally, but I think it was some sort of breather [ I have a plastic pipe I stick in that hole stops it chuffing so loudly but it is far from satisfactory and if I knew what, and where I could get one I would sort this.

Did this pump originally come with this compressor, was it part of the original set up which would make this cylinder an Ingersoll Rand too, and that would please me very much, as I then know that the cylinder would go for many more years.

Not sure what psi I should be running it at before cut out and what I should be using to run tools, so I have it set, and have for years had it set at 120 psi cut out and 75 psi cut in, giving me quite a bit free air time. It always ran a spray gun perfectly, a Devilbiss and Air Industrial Development gun, although the latter broke some time ago, it struggles with a impact wrench, which makes me wonder what CFM it shifts and whether it needs attention.

Please note this compressor has rubber anti vibration, anti wander feet and many other none standard components fitted by me, and are not as standard.

Can anyone help?


by: Roger

Looks like the inlet filter port to me.

Compressor with intake filter
Compressor with intake filter

Right now it seems like the compressor is pulling in unfiltered air. It would not surprise me if one or more of the reeds are fouled or broken, preventing full output from your machine. From the appearance of the cylinder heads, it looks like they are the same as the high pressure heads off of a larger IR compressor, so I would be optimistic that you could still source the parts to rebuild it.


Mystery compressor
by: Doug in s.d.ca.

First off, I suspect that hole is the intake – and probably had some kind of filter on it – or maybe even a remote intake, too.

Second, given you’ve changed the motor, perhaps those motors were/are underpowered. I’d think, just looking at the pump, it probably needs 3-5 HP. What’s on it now? What’s the current pump RPM?

Third, I think you probably should set the cut in closer to 95-100 PSI, which might help with the impact wrench. What pressure do you use with that? Usually they need 90 PSI or sometimes more.

Finally (well, for now), where is the output tube? It looks like it just dead ends…


Compressor and pump
by: Ray [Rob]

Thanks ever so much for your attention and kindness in answering my questions, strangely for months I could find not one picture of this compressor pump other than what I supplied, then low and behold, sods law I found one with as you say an intake muffler/filter, it seems these are, looking at this pic [ when I workout how to upload it from the site straight to here I will do so]. Model B Z31 TP49966 do these numbers/letters mean anything to anyone please?

The tank on this I/R compressor is 15” dia x 24”L which makes it 17.5 or so US gallons, rounded most probably to 20 gallon what size[ for I am looking to try and estimate what pump size this twin V is],as really I would just like to know a little more about it, maybe then the CFM can be calculated.

Can anyone be of further help please.
Kind Regards,


More detail as asked for.
by: Ray [Rob]

Compressor motor is 1425 Rpm and 2.5 hp, this is easily enough I should imagine to drive this compressor pump, just not sure what size pump this is and how many CFM it shifts, think its knackered anyway as it takes little effort to move the drive belt by hand so there seems to be little compression there. Any comments or ideas very much appreciated, may need to renew this pump, if that is necessary anyone know what it should be replaced with please.
Kind Regards


Easy to turn by hand
by: Doug in s.d.ca.

Unless you unplug it while it’s running, the unloader will be open, unloading it. So, you probably were just pulling air in and pushing it back out an open valve.

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By Bill Wade

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