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Old 08-09-2019, 10:11 PM   #1
Synchro909
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Default Rear Main Oil Leak

I know there has been a lot said about this perennial problem but I couldn't find what I wanted in my search so here goes.
I ask this on behalf of a friend.
First, deatails of his engine. Stock standard with babbit bearings and a BIG oil leak. Bearing tolerance, end play etc are all within spec but the oil slinger has been removed. Why? I don't know but it is not there! The oil groove in the rear main bearing is cut in a spiral and stops about 1/2" from the back and from the front of the bearing. I have asked him to check which way the spining crank shaft wants to take the oil in the groove - to the front or to the rear. Oil drain passage in the bearing cap and the tube are clear. The restorer replaced the slinger with a (he says) cork seal which is no longer available. I'm not able to help him there because I have never heard of a cork seal there - maybe some of you have?
My personal oinion is that his problem eminates from the seal and if they have a poor reputation, there must be a fix for it. What is it?
The other thing is "would he be better off to take the oil groove right out to the front of the bearing so oil can be returned to the sump?
The oil doesn't just drip, it flows in a stream from the split pin under the flywheel housing. Gasket between the engine block and flywheel housing is in place.
Thanks in advance on his behalf.
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Old 08-09-2019, 10:20 PM   #2
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Default Re: Rear Main Oil Leak

could he use this modern style seal that requires the slinger to be machined off?



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Old 08-09-2019, 10:21 PM   #3
Mike V. Florida
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Default Re: Rear Main Oil Leak

The cork, from what I have heard, was a "farmers fix" to keep from rebabbiting the otherwise good bearing.


I don't see what was done to make room for the cork but maybe this will help?


https://www.brattons.com/rear-main-oil-seal.html
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Old 08-09-2019, 10:24 PM   #4
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Default Re: Rear Main Oil Leak

Ouch. Is this a new rebuild from an engine builder? Or a freshen up by the owner.
If engine builder take it to him. If not....
I had one like this come in and the fix was a different crank with oil slinger on it and stock
rear seal.
It sounds like the rear main cap might have been modified also.
I think your going to have to pull the motor and have a good look.
Take pictures so everyone here can have a crack at it.

Best of luck
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Old 08-09-2019, 11:57 PM   #5
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Default Re: Rear Main Oil Leak

Options look a bit slim.
https://www.macsautoparts.com/ford_m...d-o-rings.html
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Old 08-10-2019, 10:23 AM   #6
Jim Brierley
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Default Re: Rear Main Oil Leak

We used to use rope packing as most cars did back in the 50's and 60's. The slinger could be left as-is or machined off. You might do this without disassembling the engine, put the packing in the aluminum slinger and roll into place. Pack the cap and install. Care must be used so the cap leaves no gap at the block. Good luck!
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Old 08-10-2019, 11:22 AM   #7
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Default Re: Rear Main Oil Leak

I just worked on the same problem. There was packing in the "oil seal" and the bearing cap where the slinger runs. I removed it because it was blocking the oil return hole in the cap and the part in the "oil seal" was all chewed up.
Don't know if'n it's going to help or not as I'm waiting for a parts order that includes the pan gasket.
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Old 08-10-2019, 08:22 PM   #8
Synchro909
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Default Re: Rear Main Oil Leak

Thanks guys. I've passed on these replies to the owner and he is considering his options. He is in his 80s so the minimum amount of time spent laying on his back on a cold concrte floor in this cold weather is a big factor. I've offered to help him take out the motor and put it back. He is more than capable of putting a new seal in. He is leaning torwards one of those Nitrile seals which I suspect are the reason the cork ones are no longer available (because they are better?)
BTW, The installation instructions for the seal says that the diameter of the crank once the slinger has been removed should be between 2.09" and 2.15" and as large as possible. His is 2.14" - a perfect candidate!
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Old 08-10-2019, 09:01 PM   #9
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Default Re: Rear Main Oil Leak

The cork composition seals were a pinch seal and worked OK if carefully positioned but there was no allowance for wear so leaks were inevitable as wear progressed. The rope seal also worked if there was the appropriate amount of backing to support it in the oil slinger grooves. The backing was often composed of copper tubing pushed into the groove to the proper depth. The flathead Ford V-8 engines and most engines of that era used a rope seal, which was an improvement over the slinger concept.

The newer neoprene lip seals are an improvement provided they are carefully installed and one cannot be careful enough. Testing should be done with a 30-60ml syringe placed tightly into the rear main oil feed tube before the engine is buttoned up for installation.
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Old 08-11-2019, 10:31 AM   #10
Jim Brierley
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Default Re: Rear Main Oil Leak

I've used the Burtz seal with great success, they are 1-piece, so no leak at the parting line.
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