76 2.7 case filling up with oil after full rebuild?
 

I recently purchased the numbers matching motor to my 76 slant nose tub. The original 2.7 motor was replaced with a Euro 3.2 sometime in the 90's. My close friend, a 72 y/o retired foreign auto mechanic did the 3.2 transplant and slowly rebuild the 2.7 over a number of years. After converting a 84 VW bus to accept the 2.7 he encountered a problem on the 2.7's first test run. After 20 miles, the crankcase filled up with oil to the extent it entered the bell housing and soaked clutch disc . During the trip the motor ran strong and had good oil pressure.

He split the case and checked all of the usually suspects, oil pump function, O rings, ect but could not figure out the problem. The project stalled for a number of years and recently he decided to move forward and not continue.

I have receipts which validate no expense was spared during the re-build. The case was sent to Ollie's, brand new Carrera oil pump, valve job, new pistons cylinders, main bearing, rod bolts, chain tensioners ect.

I have been reading Wayne's book trying to come up with answers. Its say that in 76 Porsche performed Oil Bi-pass modications to the case. Ike from Ollie's noted in the correspondense " your case number 6561499 shows that its a 76' case and should have the already had the oil update done at the factory, you should be good to go". Discovering this letter made me wonder. If you update to a Carrera oil pump and the case modifications were not performed could that lead to the scavange side of the pump to being able to keep up? Is a Carrera oil pump not compatible with the case? He did update the sump plate in accordance with the new pumps screen profile. New Carrera chain tensions were installed but the 911 turbo cam shaft housing oil line restrictors were not installed. Wayne's book mentions that this update "this decrease in excess oil and reduction of foaming allows the scavenge side of the oil pump to transfer oil out of the crankcase to the oil tank significantly faster"

Any thoughts would be appreciated. I am fortunate to have acquired the original motor back, with the case mods done and new parts. I have the opportunity to have a no pressure re-build just have to solve the oil problem.






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Do you have the correct relief valves in the case? When the mod is done you need to switch to the solid valves and 2 different spring lengths not the ones with the holes thru the sides.

The early 911SC's were known to have a problem similar to what you describe. There was a factory update that I believe involved switching to a different style oil sump screen. Granted your engine is not an SC, but perhaps you have the wrong style screen?

A friend of mine had the same issue. Turned out to be the end plate on the oil pump was loose. I'm sure he checked out the pump.

Since it was in a bus, I would suspect there may be an issue with the tank or oil lines between the motor and tank.

Cgarr- I will check out the type of relief valve today. Dempsey's book says the change is a must if the oil bi-pass modification was done but also states that the resulting problem will be a loss of oil pressure. Maybe that can cause the case to fill. But the motor had good pressure on the test run.

Has anyone installed a Carrera oil pump part # 91110700805 in a 2.7 case?

I have to return to the bus to harvested the rest of associated 911 parts but when I collected the motor on Monday I noticed a brand new factory oil tank and oil line to engine cooler. Unless there was a internal problem in the tank I didn't see any obvious signs of a problem in oil system parts. The installation was super clean. There was no external cooler and from what he said about the test drive there was good oil pressure and temp.

I'm excited to resolve the problem. Thanks for all of your time and thoughts. Hopefully we can diagnose the culprit.

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Here is a image of the relief valve, both are the same. Don’t see the plastic sleeve listed in the pelican kit for cases with oil bi-pass upgrade.

Apparently the oil bi-pass update happened mid 76, this is a 76 case. Is it possible that update was not done and the updated presssure relief valves are creating the problem. Can I inspect the case to check for the update?

you can see the 10mm hole drilled at an angle for the bypass when removing the spring

Olie's suggested it could be a stripped gear on the scavenge side of the pump. Maybe the brand new pump failed at the end of the test run. Has anyone tested a pump out of the engine with a tub of oil and drill or the like to turn the pump?

Anything is possible, but I'd think that if your pump failed to the point it wouldn't scavenge the engine, you'd have all kinds of shrapnel in your engine, filter, the oil you drained from the engine, etc. and it would be obvious. It's pretty easy to disassemble a 911 oil pump to inspect it though to be sure. If there is a problem with it, you'll see obvious signs of wear on the gears or the pump housing surfaces. And if you do take apart the pump, it's preferable to mark the gears so you don't lose their meshing orientation.

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Pump looks brand new. Gears turn smooth
No signs visual of damage.

Case has the oil bi-pass update.

I did notice the springs on the oil pressure relief valves were the same size and the inner spring guide were absent.
Could that cause the issue?

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No obvious signs of scrapnel of metal
Bearing seem to look good

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Is this Sum plate correct?

At a glance, your pump and sump plate look fine. Re: the pressure relief springs, I believe those are all in the pressure circuit. I am not sure about leaving out the sleeve you mentioned, but others may comment on that. Since your issue is with scavenging, I'd think something else is in play.

Random question - your oil pump was installed with the sealing rings in place, right? If those were left off for the scavenge portion of the pump, scavenging would be ineffective.

There is a thread on the pressure relief stuff that has a ton of info in case you're interested => http://forums.pelicanparts.com/911-engine-rebuilding-forum/712724-ultimate-oil-pressure-relief-valve-thread.html

Thanks stownsen, there is a tremendous amount of information in that thread.

Yes. The sealing rings were installed I remember that was the first thing the PO checked when he spilt the case..
What else can I investigate? Should I send the pump to Glenn Yee for inspection?

The oil tank was brand new wonder if it’s possible there was a restriction on the intake side of the tank not allowing the oil to leave the case. What is the pressure on the scavange side of the pump? Is it low enough that a possible restriction in the circuit after the pump could cause the case to fill?

Hopefully we can solve the mystery. I’m excited to reassemble this 2.7.

The sealing ring in #10 doesn't look to be the right size?

I just set it there when I opened the case. It would be nice if that was the problem, thank for the observation though.

Did I read correctly that this engine has been installed in a VW bus? Are you sure that the oil lines, cooler, filter, tank, etc. are all plumbed correctly?

It had been removed when I pick iit up but I assisted with the installation. The PO used a brand new Porsche oil tank and all factory lines,. Ollie’s suggest that one of the oil lines could have collapsed but upon visual inspection they appear to be in perfect shape. There was no external cooler set up.



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Two thing come to mind.

If it hasn't been done, disassemble the scavenge side of the pump and check that the key is present on the drive side gear. If it wasn't installed then it will be not operating. I have heard of an occasional issue with new pumps!

Make sure the scavenge circuit is not blocked. A defective oil filter or a stuck bypass valve @ the filter could be a possible cause.

Thanks Aaron, sure appreciate the ideas.

I will try and check the scavenge gear inside the pump, visually looking inside through the hole the gears seem to engaging smoothly and turning.

The filter was checked. How does one check the bi-pass valve? I presume it is located in the tank. I will be harvesting the oil pump out of the van early next week.