Experience with Oil Pump Remanufacturing

[LDunville]

I'm about to replace my oil pump on my 1968 911S. Mine's passable, but with a total rebuild, I think I should be replacing this too. After all, what's another grand or two !?!?!

I've already has the case machined by Walt at Competition Engineering at which time he perform the case modification for the overflow.

The new pump is $1350 from Stodard's but I've found a source that rebuilds them for $350. Here's their web address:

https://www.partsklassik.com/Porsche...FfBaMgodVWoAFA

I called the company and the person I talked to sounded very well versed.

Anybody have any feedback or experience with oil pump rebuilds???

Thanks
Larry

[ajwans]

I'm pretty sure I paid less than that for Supertec to do this job.

What type of pump are you using? To get the benefit of the oil bypass mod you should use a pump with a bigger pressure side and a smaller scavenge side as there's less scavenging work to do.

andy

[304065]

I'm about to replace my oil pump on my 1968 911S. Mine's passable, but with a total rebuild, I think I should be replacing this too. After all, what's another grand or two !?!?!

I've already has the case machined by Walt at Competition Engineering at which time he perform the case modification for the overflow.

The new pump is $1350 from Stodard's but I've found a source that rebuilds them for $350. Here's their web address:

https://www.partsklassik.com/Porsche...FfBaMgodVWoAFA

I called the company and the person I talked to sounded very well versed.

Anybody have any feedback or experience with oil pump rebuilds???

Thanks
Larry

Larry,

I would be cautious in this area-- I changed to a late four bar pump with the larger pressure stage and have had very high oil pressure as a result. There is actually an admonition in the factory manual that says don't change to a larger pump in the early engines. Perhaps this is for clearance issues.

Since you will presumably be going to new bearings as part of splitting the case, you can calculate, and also measure, the as-installed bearing clearance. If you have 0.002-0.003 inch clearance as installed, you could end up with high pressure at least for a few thousand miles until things break in a bit.

You should do the oil bypass mod and the piston squirter mod, these are good insurance, and do the rest of the mag case mods while you are in there- presumably your case is a 0R or 1R so it could benefit from state of the art.

What is the condition of your current pump? Take some digital photos of how it goes together, then remove the four M6 nuts (10mm atf) that hold the pump together. You can then look inside at the gears. You are looking for damaged teeth. Next, measure the gear length and compare it to the length of the housing-- you are trying to get a sense of the end play in the gears-- obviously as a positive displacement pump, oil that goes between the end of the gear and the housing is bypassing the pressure. Some actually use plastigauge to measure this. You can surface the end of the housing using some sandpaper that has been glued with contact cement to a) a granite surface plate; b) a sheet of thick glass or c) your kitchen counter when the other Dunvilles are out at the ball game. Don't take too much off and check your clearance frequently to make sure the gear doesn't bind.

As far as improving the flow, I think the mod consists of smoothing the outlet from the pump with a grinder-- I have no way to validate the claims of improved flow and have never seen or set up a test rig for the pump. Being a positive displacement type the pressure ratio is all about the length of the pressure stage. The oil bypass mod on its own will help by reducing the standing oil level in the case, should be good for a measurable power gain on the dyno due to windage.

I am highly skeptical of the claim on the partsklassic web site "modified so that the case will have to be modified to prevent it filling with too much oil." What I THINK the author is suggesting is that the enhanced flow rate of their pump will put so much oil through the engine that the oil level will rise in the case because pressure flow is so much bigger than scavenge flow. But their mod doesn't change the size of the oil passages in the case, so effectively a higher volume of flow will result in higher pressure, unless you have other case mods like piston squirters that are flow consumers. Also, presumably if they can modify the pressure side of the pump for better flow, they are doing the same to the scavenge side so it can keep up.

The oil bypass mod DOES reduce the level in the case by diverting bypass oil pressure >77psi back to the inlet to the pressure side of the pump vs. dumping it into the case. This allowed Porsche to make the scavenge side of the pump smaller and the pressure side larger, all within the same length of pump in the case.

If you do use the later pump, be sure to get the venturi screen that goes between the case and the sump plate. This replaces the original wire mesh screen that is on there-- it only fits on the studs one way-- and this helps de-aerate the oil as well as providing a better scavenge pickup.

For more information than that, see my expanding web treatise about oil systems here:

http://forums.pelicanparts.com/911-e...ve-thread.html

Hope this helps- some photos would be great!

[kenikh]

I'm running a 4 bar in an early Al case, excellent oil pressure, no clearance issues.

[ajwans]

As far as improving the flow, I think the mod consists of smoothing the outlet from the pump with a grinder-- I have no way to validate the claims of improved flow and have never seen or set up a test rig for the pump. Being a positive displacement type the pressure ratio is all about the length of the pressure stage. The oil bypass mod on its own will help by reducing the standing oil level in the case, should be good for a measurable power gain on the dyno due to windage.

Terrific post John, as for the port modifications, aside from smoothing the sharp bends around the oil inlets and outlets they also remove the negative draft angles left when the bodies are cast.

andy

[Merv]

I have no idea on mine. I can understand how critical oil pumps are but how do you test the output?

[kenikh]

IIRC, you need a rig to test it, which entails:
An electric motor capable of setting RPM
An oil reservoir (5 gallon bucket)
Flex tube that fits the outlet hole on the pump

you then jig up the pump and run it run it for a minute and measure. The liters output in 1 minute.

[Silverbullit]

I'm pretty sure I paid less than that for Supertec to do this job.

What type of pump are you using? To get the benefit of the oil bypass mod you should use a pump with a bigger pressure side and a smaller scavenge side as there's less scavenging work to do.

andy

So, are you saying the bypass mod is worthless w/out later pump, or can it be done on, say, a 67 w/ stock pump? And would there be any benefit?

[304065]

So, are you saying the bypass mod is worthless w/out later pump, or can it be done on, say, a 67 w/ stock pump? And would there be any benefit?

The bypass mod on its own will lower the level in the case. It is recommended if you have the case apart.

[ajwans]

A benefit of the oil bypass mod is higher oil pressure, but only if you have a bigger pressure side to your oil pump.

andy