Rear main bearing cap oil return line question
 

Oil is running out of the rear of the rear main bearing cap, travels down the bottom of the cap and out of the dust cover and flywheel housing cotter pin. I finally got the bearing cap off tonight (engine is still in the car with a counter balanced fly wheel). Took out the soft plug and looked at the oil return pipe. It is screwed all the way in to the end of it's threads, with a considerable amount of threads showing in the galley behind the soft plug. Okay, here is my question...was the return pipe in further than it needed to be causing my oil stream? It's not my car so I don't know the history. And the galley is not plugged nor is the pipe. I have purchased new pipes and soft plugs. It looks like it's the 3/8" pipe.

Re: Rear main bearing cap oil return line question
 

I'm not familiar with any "soft plugs" being used anywhere near the rear main bearing cap. Where was this plug? Can you provide a picture?

Re: Rear main bearing cap oil return line question
 

might want to check crank end play if it is excessive it will act like pump and it will leak

Re: Rear main bearing cap oil return line question
 

Have you checked the (rear main) bearing clearance?

Re: Rear main bearing cap oil return line question
 

Is the crankcase free to breathe? If the oil cap is pressed on too far or something else restricting free venting of the crankcase, it will push oil out the rear main. Not that you haven't found another cause but restricted venting will confound any repairs that you make.

Re: Rear main bearing cap oil return line question
 

For those who may not be familiar ...

Also the end of the tube must be long enough to go below the lowest level of the oil (like when a quart or more low) in the pan in order to prevent back pressure from forcing oil out the rear main.

Tubes are 4 inches long end to end as I remember.

Re: Rear main bearing cap oil return line question
 

I was told many years ago by an engine builder to be sure the drain pipe does not go into the cap too far.

Re: Rear main bearing cap oil return line question
 

There is a Welch Plug that is 90° perpendicular to the drain tube that is used that some call is a soft plug.

Re: Rear main bearing cap oil return line question
 

Ah! thank you. I found a picture that does show this. I never realized it was a plug, but I can see it's needed to drill the passage from the groove to the drain tube.

Re: Rear main bearing cap oil return line question
 

That's correct.

It is good practice to remove the plug during cleaning when the engine is rebuilt to ensure the passage way does not having any material (bearing material, sludge, etc.) that could restrict the oil from flowing out of the cap.

Re: Rear main bearing cap oil return line question
 

Ok I have more to add to the story...I removed the drain pipe this evening and found some sludge in the galley under the bearing cap. Not packed tight, but enough to slow things down. That would make sense since I found some sludge in the pan under the dipper tray. Has anybody on here used the return pipe with the V notched in the top of the pipe at the threaded end?

Re: Rear main bearing cap oil return line question
 

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Re: Rear main bearing cap oil return line question
 

There is some back and forth play but none for up and down.

Re: Rear main bearing cap oil return line question
 

It's good, no restrictions and no blow by.

Re: Rear main bearing cap oil return line question
 

Yes I had a conversation about that with Herm Kohnke when I picked up my motor from him. This isn't that motor.

Re: Rear main bearing cap oil return line question
 

No I haven't yet, it will be a challenge to do as the engine is still in the car and the crankshaft is counter balanced. Working thru the dust cover does not provide any extra clearance that is for sure.

Re: Rear main bearing cap oil return line question
 

My opinion on this is the welch plug needs to be removed and that area fully cleaned using a bore brush and flushed.

Next, forget about a Vee-notch in the tube and install it the correct way. The Vee or a notched groove tends to make a dam that only creates issues, -especially if some debris was to get into the galley there. If the tube's threads are loose in the cap, either use JB Weld or Loctite 620 to hold the tube in the correct location. The correct location is determined by sighting into the hole where the welch plug seals and making it as-close to flush as possible and still be oriented the proper way at the tube's exit.

Re: Rear main bearing cap oil return line question
 

I tried the V notched tube before I read your post. Could not get the thread to start properly, wanted to cross thread. Got out the stock replacement one I bought from Snyder's, went right in. It tightened up real tight on the last turn in and it is flush with the bottom of the galley. Feeling really good about this, I have the cap in but only finger tight. Next question...what, if any, sealer do I use under the cap or shims?

Re: Rear main bearing cap oil return line question
 

I used a pistol cleaning bore brush and blew out a few times with 115 psi air. She's clean as a whistle!