oil pump dismantling

Pellesin · 10:57 AM

Hey!
Is there anyone that has dismantled and rebuilt an engine oil pump?

I'm reassemblying after a rod big end bearing has spun. So naturely I'll have to make sure that the pump (along with allot of other things) is perfectly clean. How does one do this without opening it?

If I understand mr Dempsey's book correct he does not recomend opening the pump because it's possible to reassemble the gears so that the gear teeth engagement is altered. The teeth are worn together, and if all of a sudden the teeth are "introduced with a new mate", they might not fancy that allot.... when he talks about reassebly though - he states that the pump should be cleaned.

So my question is: how hard is it to keep track of this. In my mind it should be possible to just mark the opposing gears tooth and groove on the scavench pump and then the highpress pump so that you can verify that the gears are mated properly back together.

Any thoughts?

What about gaskets? Are they supplied in a bottom end gasket kit? Are there any gaskets?

ajwans · 03-11-2015, 11:22 AM

It's a pretty simple device. Just punch the pins out and undo the 4 nuts. When taking the body apart do it so the scavenge tube end is up so that the gears inside don't drop on the floor.

The ends of the gears have been punched with a mark on the units I have taken apart. If not, now is the time to mark them and photograph the orientation.

There are some good threads on here regarding how to refresh the pumps so I won't repeat them, use the search instead. You can also grind the ports for better flow, also covered in this forum.

There are no gaskets on the units I have rebuilt.

andy

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by ajwans

It's a pretty simple device. Just punch the pins out and undo the 4 nuts. When taking the body apart do it so the scavenge tube end is up so that the gears inside don't drop on the floor.

The ends of the gears have been punched with a mark on the units I have taken apart. If not, now is the time to mark them and photograph the orientation.

There are some good threads on here regarding how to refresh the pumps so I won't repeat them, use the search instead. You can also grind the ports for better flow, also covered in this forum.

There are no gaskets on the units I have rebuilt.

andy

We do a pump rebuilt and flow modification on your pump, exchange or we sell them outright.
Pumps are on the shelf at 911Vintage Parts.
760-731-4911

Pellesin · 03-11-2015, 02:25 PM

Thanx Henry and Andy for youre quick replies

With regards to the pump I have I belive it performs quite well. I actually get (or got before I dismantled the engine) more than 1bar pr 1000 rpms. This can of course be related to the oil pressure regulating spring/piston being stuck. I`ll check this when I get the crank case back. (I used the case as a transport "cradle" for the crank as it is shipped for machining.

As I like to find out if parts are really broken before I replace them (cheap bastard ehhh) Is there a way to make a performance test?

The oil pump it self spins along with the IMS - which inturn drives the cams = 1/2 engine rpm.

Is there a chart somewhere with lets say: oil pressure on the vertical axis and rpm on the horizontal axis. That would reveal good-ok-bad pump? (oil press vs rpm)

So If you connect the pump to a drill and submerge it in oil - connect a pipe with a pressure gauge - this will be tricky I admit but if I`d manage something like this I can verify wether the pump is performing good or not.

Henry: Do you perform a test like this? Not a "redneck approach" like mine but a professional performance test?
You of course do not have to answer this question - It`s youre profession and I fully respect that you wouldn`t give up any "tricks of the trade".

best regard
Pelle

chris_seven · 03-11-2015, 11:36 PM

Oil pump testing is quite involved and we have just started work on a pump test stand.

We have bought a suitable electric motor and an inverter drive as the prime mover and have started to fabricate a simple frame.

We still need to make a tank with an oil heater as flow vs temperature is an important parameter.

We will incorporate a torque measuring system so we can check the horsepower consumed by the pump.

Frictional losses in scavenge pumps can be particularly significant.

Pressure measurement is quite easy but flow and suction will be a little more complex.
I have never seen any published data for 911 pumps so we will have to bench mark using a selection of pumps that we have in stock.

I am interested in the flow increase that can be obtained. Is this on the pressure or scavenge section of the pump?

Henry Schmidt · Henry Schmidt's Garage

We built a test bench back in the 80s (when we first started modifying pumps) that used an engine lathe as a drive mechanism.
The results of our testing was about 15% improvement on cold flow at 3000 rpm pump speed on the pressure side. We saw no good reason to test the scavenge side.

racing97 · 03-12-2015, 07:27 PM

Chris I seem to remember seeing roughly 12/13 gpm @ 6500 flow measured with a Turbine flow meter, and I believe that a front oil cooler system requires 50 psi to circulate so the scavenge side will require some engineering and perhaps will be the most rewarding of the parasitics.

chris_seven · 03-12-2015, 08:07 PM

I would have thought that the scavenge side losses occur and improvements could reduce the power needed to drive the pump.

I have a colleague that designs Dry Sump Pumps but mostly internal gear pumps and we are mainly building the test rig for these pumps but it may be interesting to measure some 911 pumps.

I am not sure about the power needed to drive a 911 pump but I can imagine that it is between 1.5 and 2.0 horsepower