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915 Nose Cone Cooling Pump Housing - Acceptable Wear?

How much wear is to much or what is typical expected for the pump housing? I have a machined nose cone for a 915 for the built on 915 RSR/RS oil pump. Its a mag case so its a soft metal from the get go. The pump housing has some wear around the circumference of the pump typical of pumping unfiltered oil. The grooves can be felt with a finger nail but not excessively deep. If this was an oil pump for my engine I would probably buy a new one since wear = less pressure. This pump is designed to pump and circulate oil to a cooler and to the gears via the spray bar. Im sure it still pumps plenty of oil to still do that. The gears look great so no problem there. The gears also spin freely inside the case.

I thought about having the housing wear filled then honed. Im not sure its economically viable. Is there a filler compound that can be used to accomplish this? Option 2 is to buy a new nose cone which isnt cheap nor having it machined again either. Or option 3 is to just not worry about it. I cant say I have seen many of these and if its typical wear or not.

Thoughts?






Last edited by tocobill; 03-15-2018 at 09:09 AM..
Old 03-13-2018, 07:22 PM
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This got buried quicker then I thought ... Bump.

Any transmission gurus have thoughts or running these components that can weigh in?
Old 03-15-2018, 08:40 AM
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Ken Wunsche
 
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You might look around in the 356 world. The engine oil pumps were similar, driven off the end of the crankshaft with the pump gears located the the aluminum housing. I have not worked on a 356 engine in a long time, but I don't think that amount of wear is that critical. Also engines use 30/40W oil, transmissions 90W.
Old 03-15-2018, 11:01 AM
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Ken Wunsche
 
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Looking again at the pictures, check the shaft play. You might need to replace the bushings.
Old 03-15-2018, 11:04 AM
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Thanks. I will most likely press out the bushings and turn a new set. Not much play but some grooving that I don’t care much for. Funny Porsche wants ~$50 each for a simple bushing.

Good point on the oil. Ill take a look at the 356 sites to see if I can find any relevant info.

Last edited by tocobill; 03-15-2018 at 05:00 PM..
Old 03-15-2018, 11:30 AM
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How are you using the car? I am tempted to say that if this is a street car, don't worry, you don't need the cooling / pumping. If otherwise, ...
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Old 03-15-2018, 07:20 PM
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How are you using the car? I am tempted to say that if this is a street car, don't worry, you don't need the cooling / pumping. If otherwise, ...
Its going in an RSR clone. The more I look at the housing the less concerned I am of it. Ive seen oil pumps that look far worse and still put out plenty of pressure. The problem is I havent seen enough of these to know what normal wear looks like in this duty.

Im curious what the pumping rate was designed to have for circulation of oil? With that info I sure it could be bench tested for flow and pressure.
Old 03-15-2018, 07:47 PM
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What do the rotors look like? That almost looks like tool marks. Was this a tailcone that was converted more recently or an original factory one?
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Old 03-15-2018, 08:44 PM
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What do the rotors look like? That almost looks like tool marks. Was this a tailcone that was converted more recently or an original factory one?
The rotors look good. They don’t appear to have any pitting or look like metal went through them. The faces are clean and no burrs are present on the tips. My experience with spur gear pumps is they spins so that the oil flows around the outside of the pump instead of through the pump. So any wear is on the circumference is the housing or if it sucks crude through the pump it will groove/imprint on the softer material ie the housing.

It doesn’t appear to be a recently converted cone. It’s an early housing. Mech Speedo. The drive gear is an earlier version that had the solid pin vs u shaped groove cut in it. So it would be 915/40 or earlier since the 915/44 was electric speedo? Date code on the cone is 12/76 ... which confuses the speedo drive therory. I’m not sure when the change happened with the drive gear.

Last edited by tocobill; 03-15-2018 at 09:21 PM..
Old 03-15-2018, 09:10 PM
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These are the only pics I could find of similar parts. Both are 916 transmissions with rs pumps.

This picture shows some of the same markings I have if you look close. Case appears to be magnesium.


This one appears to be aluminum or magnesium and very little wear.
Old 03-15-2018, 09:53 PM
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That scored area looks a lot like my 964 pump housing that ingested a bunch of bearing material.
So it definitely looks like debris damage to my minimally trained eye.

Engine Bearing Failure- Disassemble Heads Too?

Maybe it could be machined oversize and then a partial/crescent steel sleeve could be pressed or staked in place. Unfortunately there's not a lot of thickness in the housing on one side. But I don't think the sleeve would need to be exceptionally thick. It's not like this is a bearing bore where it's subjected to heavy loads.
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Old 03-16-2018, 08:39 AM
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That scored area looks a lot like my 964 pump housing that ingested a bunch of bearing material.
So it definitely looks like debris damage to my minimally trained eye.
Same thought here. So how much is acceptable? This thing operates much like a scavenging pump. Iím sure it will still pump no problem circulating oil and enough pressure for rp cooling.

I think Iím going to bench test it with some buckets of oil to get a pump rate. If it lifts the relief valve at speed or the flow spray looks good Iím going to give it my blessing. Iím sure this is going to make one hell of a mess.
Old 03-16-2018, 09:01 AM
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The gears do the work of delivering the oil. Oil gets paddled around the housing by the rotation of the gears. The oil itself seals the tip of the gears to the housing. If the clearance (or scoring) with the housing is too big then the paddled oil escapes.

This video is a good one to show how the gear mesh pumps work. The guy mentions at around 8:00 how it works and briefly says the pump is hosed if the housing is scored.

https://www.youtube.com/watch?v=TIGSBEUGYeU

That's obviously an issue if you need a pump to build substantial pressure. Well since you don't really need pressure here per se', I don't think it's a big deal. As long as you're still getting ample flow out of the pump, despite the losses that are occurring due to the scoring, then you're still able to accomplish what you want to and that's get the oil sent out to the spray bar. However, if the restriction caused by the spray bar are such that the pump continues to "bypass" oil through the scoring? Then it's not going to deliver as much oil as you want it to.

So I guess my uneducated answer is, it depends. I think it's a good idea to test it and see what kind of oil delivery it makes through the spray bar. I think the key is to put a restriction on the output side of the pump to mimic the spray bar and cooler.
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Old 03-16-2018, 09:34 AM
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Thanks Kevin. I think you and I are looking a the this the same way.
Old 03-16-2018, 09:45 AM
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