Here's the deal,
The rear main ( rope )seal on my 56 Old's has started to leak, its not terrible but enough that I wouldn't park it in a friends drive way (if ya know what I mean ) There was a time I would have tackled this my self but age and physical limitations are taking their toll so I'm no longer able. I don't like leaks so I started scouting places that would do the job, not many takers !! there is a place very close by that does standard veh care but the owner also works on street rods, resto's and classics, I stopped in to talk to him and here is what he told me, he stated the obvious, to do it right the eng has to come out. ($$$$$) he says he can do it but recommends I live with it, he says its been his experience it will leak again, maybe 6 months down the road, maybe a year but it will leak again especially if the car does not see a lot of use. He said look the car has a draft tube right ? (the answer is yes ) so you keep a drip pan under it anyway right ? (the answer is yes) he just recommended high mileage oil and maybe a 20 w 40 or 20 W 50 oil ( we are in AZ.) He didn't think the cost justified the result. What do you think ? we didn't get in to pricing but his classic/street rod labor rate is 145 per hour. I have had two rope seal experiences where I replaced them BUT in both cases I sold the cars after I did the work, the rope seal repairs were successful for the short term while I still owned them, P/S I don't know if there is a suitable neoprene replacement available.. Hmmmm not sure which way to go.

 

It would have to be past leaking for me to pull the engine and have it pulled. I probably still have a tool to install rope rear main seals. I has a thing on it like those things you used to put your finger in and it tightened down when you tried to pull your finger out. I have had it a long time and can't remember having a car I bought it for. I loaned it to a friend once but I know he returned it. I assume they still make them. I believe you can replace the seal without pulling the motor. I would put cardboard under the engine and monitor how much it leaks. It is really had to get one of these old cars to where ti doesn't leak.

 

My Jeep rear main was dripping for a few years, and I read on the Jeep forum that a lot of Folks had success using high mileage oil. I tried some on my next oil change and the leak stopped soon afterwards.

 

I've successfully repaired leaking rope seals without pulling the engine but they were the next Gen Olds. We packed the upper seal tighter, replaced the lower half of the seal and they didn't leak. Due to the age of the rope seals I would not recommend packing the upper seal tighter. My suggestion would be to fabricate a catch can or pan until it's leaking enough to make it worth replacing the seal. It is very unlikely that it will suddenly leak excessively, expect it to gradually leak more at worst.

 

Yes, there is'
And it's a much better deal than a "rope" seal.
See the link below;
New 1949-59 Oldsmobile 303 324 371 1955-59 GMC 324-370 modern Rear Main Oil Seal | eBay

 

Thanks for the link.

 

PCV valve creating a bit of a vacuum could help.

 

You're welcome.
I've got a similar one in my 394, doesn't leak at all.
"Rope seals " are "old farm tractor" technology.