911/41 oil fills crankcase just sitting over night

[917Chris]

I've got a 1974 911T motor in a kit car that I have been working on little by little. The engine leaks oil like crazy when I got it. It has not been running for several years while I work on it...
One of the things I did was remove the original oil tank that someone had mounted to the side of the engine and put a smaller oil tank mounted above the engine with an oil cooler added to the oil return line. With a total oil system capacity of 8 quarts.
I filled the system with oil by filling the tank while turning over the engine slowly until i got oil all the way back to the tank. I did a compression check but did not start it.
The next morning the engine is dripping oil, I remove the engine drain plug and a little over 6 quarts of oil comes out 'of the crankcase'.
Everywhere I have looked, nothing is said about oil tank height in relation to engine...
Do I have a really worn out oil pump or is the height of the oil tank a problem and if so what should it be....
Thanks, Chris

[bkreigsr]

Are the cylinders filled up with oil?
(Don't try to turn the motor over with the plugs in.)
Otherwise, what you are saying about the six qtrs. draining out of the sump sounds normal, (aside from the puddles on the floor). Mine will do that if I don't drain the oil tank first.
Most air-cooled 911's have the tank's drain plug mounted about 6-8 inches above the sump drain plug.
Hopefully, someone that knows will chime in before I lead you too far astray.
Bill K

[db_cooper]

911 engines will "wet sump" once parked for a length of time..maybe over-night or a few days.

It is normal..gravity will pull the oil through the bearings and pump..normal.

Porsche knew and made the scavenge side of the oil pump side twice (or more) larger than the pressure side. Once the engine is started the scavenge side of the oil pump clears out the crankcase in a matter of seconds.

Your oil tank position will have little to do with it..your engine will "wet sump" anyways.

[917Chris]

No oil in the cylinders and I have the plugs out and can see in.
Here is what my setup looks like.
Remember the return line runs up to an oil cooler in front and than back to the oil filter than the tank.

[gomezoneill]

OMG!

[Walt Fricke]

My track car with the oil tank in front, and the return line run through the hot air ducts and thus getting up above the chassis arch over the drive shaft, acts like pretty much every other 911 - the engine sump has plenty of oil in it when I drain it. So this is only an issue if you are getting oil into the combustion chamber, and you aren't.

However, you might look to see if our host sells the Rothsport valve which prevents the gravity (and syphon) flow from the oil tank to the oil pump. It is a low cracking pressure valve, so when the engine starts it readily opens because the suction of the pump is more than enough to do that. It is made for the ID of the stock large S shaped rubber hose from the stock tank to the inlet under the oil cooler, but you obviously have the ingenuity to deal with things like that.

[917Chris]

Thanks everybody,
It just seems like too much oil,
Walt Fricke, your idea of the valve sounds like the way to go.
Than maybe it won't leak so much as well..
Hope to do a rebuild on the engine next winter.
Right now I'm happy to have the body back on and working on the body and interior.
Anyone interested can see my progress, Rebuilding our 1972 Porsche 911 with the 917 style body.

[SoyRacer]

I've had this problem before. Where does the bulk of the oil come from when it leaks?
I've had a few long term sitting cars that developed large puddles of oil under the cam tower areas. The culprit in both cases turned out to be warped magnesium rocker covers. When the oil reached a certain level in the engine it would leak out of the lower covers. The oil tracked as though it was coming out of a rocker shaft. If it sat for a week, not a single drop but for a few weeks and you'd have a quart on the floor. I replaced them with aluminum, turbo upper and lower covers . . . they never leaked again.

A possibility-

RR

[Walt Fricke]

Soy - it is puzzling, isn't it. Not only does oil, under only gravity pressure I suppose, have to get by the pump gears (no sweat, they have a clearance which has to be larger than one oil molecule), they then have to travel up into the main oil gallery (which is on top of the engine), and then down to the crank to leak out of the #1 or #8, or maybe through the crank to the rod bearings.

An alternative leak might by past the piston of the overpressure system, which is low down and empties into the sump. The sump exit is closed with the engine off (and should be with the engine on, too), but it's tolerance is not as close as, say, the CIS control piston which is individually fitted into each fuel distributor. And the ends of the pump gears are not sealed against the ends of the housings, and the shafts on which the gears rotate are not sealed and its front end is exposed.

Despite the apparent mystery, the presence of this oil is a fact, so it is our ignorance (of something we don't really need to understand) which is troubling, not some unknown design flaw of the engine.

[Eagledriver]

That tank design looks like it would not work well handling corners. In right turns the intake line to the engine looks like it could starve

[Walt Fricke]

Yes, I like to have my tank tall and narrow, so there is a maximum head above the outlet. There is room for that back there.

[917Chris]

I see what you mean, I'll need to figure another tank. Thanks I had not thought of that.... :-)

[917Chris]

Oil pretty much comes from everything, covers and drain tubes mostly. The entire engine was covered in old oil grim, cooling fines were even plugged up. I have cleaned it as best I could and I've been putting together parts for a rebuild. Already have new barrels, pistons and rings, mostly need a full gasket and seal set plus may as well do the clutch while I have it down. Hoping to do that this next winter.
I looked into the Rothsport valve, great idea and looks like the way to go.
But $300 for spring loaded check valve is not in my budget, I'll have to figure out how to make one.
Thanks for all the great help everybody....

[BoxsterGT]

The later, water cooled, REAL (Metzger ??) 911 motors have an oil tank above the Rt Forward corner of the motor. I believe it has a check valve to keep the oil in the tank.

You might want to look into that design for your application.

Len

[917Chris]

Thanks BoxsterGT, The check valve is what I'm working on, I just can't afford the $299 one suggested . I think I can figure one out.
Thanks everybody.
I did a couple other replies that did not get posted. Hope this one does... :-)

[917Chris]

917Chris
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