My rms is leaking again.  I hv cked all other options for leaks and its none of those.  Ie, oil presdure, valve covers, etc.  

So i called egge to order another one.  I asked the guy wat contack cement is required. He didnt know. Told me to call Roy at best gasket.

Surprisingly, he ansers the phone. So i went through the speil that many of of have had regarding RMS.  He said that this seal is one of there most leakfree seals.   Sells 600 plus a year.  

He did say, that if the engine had been line bored (??) They are more inclined not to work as it becomes sinorly out of round.  Im guessing he means changing the diameter of the crankshaft during builds.  I told him mine had only been polished.  

I said well whats the solution?  He said many peoole are using a shim ( i think he said a 20000th thick or maybe 2000th thick) piece of paper that is inserted into the groove so as to provide a little more pushing pressure against the crankshaft to seal the oil off.  He said some use it on both top and bottom of bearing cap, but some just lower. I guess depending on whether crank is out of engine or not.  He also said they do not suggest using sealnt or cement on their ends, but that many offset the ends into the ends into the groove.  He is mailing me a couple of those shims.  For those way more knowledgeable about engines. If you have more detailed questions, ypu might call him.  Hecwas quite patient with my questions, but for those of us been chasing this leak awhile, it could be part of reason why.

Just thought i throw all this out for fodder

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It was myself who was chatting with someone who used an original NOS seal from National.   My rear main seal is now leaking, just like the rest. 


Thank you 

I do assume a rear seal from National is difficult if not impossible to find today 


Doing some  64 rear seal research  myself ——-I was directed to a thread on the Cadillac Lasale  web site that a —-1965  manual supplement indicates —-that Cadillac changed the rear bearing  design  in  the 65  429 that now has a grove placed in it —- to allow the oil to drain into the crankcase and removes the pressure on the 64 rear main seal 

That was brought to the attention of a person who posted owning a 64  429 that had a bad rear crank seal leak on that site 

Could a replacement 65 429 rear crank  bearing  (  different grove design than the 64 429 ) be the answer we are looking for to end this leaking seal issue ?

I would like to find that 65 manual supplement to look into this interesting info—- about a 65 rear crank bearing new change in its design 


I do see that the serviceman Cadillac publication index for 65 does address the oil pan and rear bearing issue on page 11 —-but I do not have access to that physical info myself 

Anyone who has access to that info can jump in and verify that it indicates a bearing design change in the 65 429 rear main bearing which could be the answer to our never ending rear main seal leak issue 


I put the call into BestGaskets and spoke with the girl that answered the phone 

She told me the boss would get back to me ——but has not in two days 

I hope others made the call 

I am realizing with people doing this replacement seal 2 and  3 times ( Kim is on his 5 try )  with  very little results costing in the area of $50 dollar a time for just the seal ( not to mention a pan gasket and much labor involved ) that Bests Gaskets is —-making a killing in the market —-selling these gaskets that are the only one available for our cars when I looked 

That  profit margin could be effecting his plans to be redesigning and improving the seal so that it works as it should to stop the leaking after a new one is installed 

Looking forward to finding out —if the shim with the seal will correct the leaking  when someone uses that method in the future 


Hi Tony,   did you ever get a call ftom best?


Was told Best Gasket would call back a second time on Mon but he did not by person that answered the phone ( twice ) 

Any thoughts on the  Serviceman publications  showing the redesign of the rear crank bearing on the 65 429 that added an additional grove to that bearing to reduce pressure at that location some time in 65 ?

This seems to be Cadillacs correction for the seal leak issue —-only available in the 65 repair publications —and the reason many are not aware of this change as it is not in any 64 repair publications 

Do you by any chance remember— if your rear crank bearing in your recent engine rebuild had one or two oil groves in the rear  crank bearing ?

Love to know if all new replacement crank bearing available now have the additional grove in that bearing due to Cadillacs 65 update 

Tony.   Picture of my rear cap from old 63 engine.  If you remember bk when i did this year or 2 ago,  Mark Anderson pointed out that cutout in my cap.  You can see it in the picture.  He had thought it coub hv been cause of leak, but since it didnt cross all way over, he concluded probly not.  Dnt know if this picture helps your search

So now you did have the two groves in the rear crank bearing and were still not able to prevent the leaking 

I think you engine had been rebuilt once before ( as I think you had indicated ) so that might explain the newer bearing design 

I do not see — the  important cut —they made in the Serviceman’s publication  at the top of the bearing ( from front to back ) that is the passage that allows the oil from the second grove to reenter the crankcase in your picture ( a very important cut ) 

If you go to Matti Roth’s  post  —the picture of his crank bearings he has two holes at the bottom of his one grove  bearing that you do not have in your  rear crank bearing that would be returning oil to the crankcase 

Thanks for  the photo as it help some to understand a bit more about what is going on with these rear crank bearings 


Yes, it had been rebuilt in late 90s, but i dnt know who put those two cuts in there

I am very sure that the new bearings at the time of the 90’s rebuild came with the two groves in them 

Those groves are the same from manufacturing 

If you go back to the Serviceman  from 65 info I posted you will see an additional grove that it suggests to be cut in the top corner of the bearing and end cap 

Follow the arrows that come up the second bearing cut and make a left turn at the top of the bearing  putting the oil back into the oil pan in the picture in the Serviceman info 

That left turn cut  needed is what you are missing possibly on your last engine rebuild ( hope you have the two grove bearing in that build )

I think you need to have that cut  ( the one from the front to back on the top ) made by a machine shop to flow the oil in the second grove back into the oil pan thus removing the pressure in the second grove and the rms 




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