Surprised no feed back on the 65 429 rear crank bearing redesign change Service

As the  rear crank bearing was redesigned in the 65  429 by Cadillac to reduce pressure on the RMS I thought it might be the answer to our endless leak issue many are having 

No one has found a solution to be stopping the leak completely 

Could this issue —-just be past history —with all the new crank bearings from that point forward now being available with that redesign ?

Does anyone who has recently replaced there crank bearing recall if that second oil grove  in the rear crank bearing is now always available with new replacement  bearing parts ?

If the new replacement bearings do come with two slots cut in the rear main bearing for additional oil drainage then our oil seal leakage issue —-is not solved and will still remain an issue for all doing this repair 

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Headline should read —  in the Serviceman's publications 

Hit the— the Add Reply by accident 

If the new bearings  do come with two groves in the  rear crank bearing since  the 65 redesign  the rear end cap —-will still need to cut for the oil flow to return to the crankcase to relieve pressure there —if a 64 engine block 



I have replaced the rear seal during rebuild project but engine is not ready yet. The new one is from Best gasket, the old one had just number 1480876 so probably it was the original. It was very hard and probably not sealing much anymore. I do not know if it was leaking when engine was in place.

I did not replace bearing as it was in good condition. Only one groove there  


Is it reasonable —-that your rear crank bearing ( which is still good ) and the seal you removed are original stock parts to that engine block ?

Is you engine a 63 (390) or a 64 ( 429)  which would be the same engine block so all info applies to both 

If so this is confirming my thoughts that there are possibly many  63 64 stock blocks that only have one grove in the rear crank bearing —and have not been updated to the redesigned 65 two slotted crank bearing  to be reducing the pressure on the rear crank seal and reducing the oil leaking possibility 

The next question is whether —-all new bearing sets —since the 65 bearing design upgrade  come with a rear crank bearing with the updated two grove design ?

Glad that the timing of your current engine build has  provided the info it has in my quest to try to get this  rms leaking issue solved for the community 

You may be one of the first engine builds to benefit from the info just confirmed by the 65  Cadillacs Serviceman’s publication regarding the rear bearings design 

Sure you read the post  by Kim about using the shim that the owner of Best Gaskets has recommended using when installing a new Best Gaskets rms ( brand new recent info from the owner regarding the shim use ) 

You could be one of the first engine builds that have this info available to them and can apply it 

I will be following your engine build closely to see what you do with the info and the end result once the engine is in the car and running for the end results which is hopefully — no oil leakage ( you would be the first I know  to accomplish that since I am here since 2006 daily ) 

My guest to possibly solve this leak issue  is exciting to an old gear head 


Contact Best Gaskets  owner directly — for the shim they are recently  recommending using with the new replacement  rms 


I was going to use original crank bearings but if I want to avoid the leak I should use the bearing with extra groove. And if I do that, I need to buy the full set of main bearings so I could change all of them. I already have pistons and timing chain in place so I am hesitating do I want to reverse in project. Probably I should. Easier to do it now than when the engine is in the car.

My understanding from reading the Serviceman article is that only the rear bearing needs to be replaced with the new double-groove bearing. The chamfer must also be filed into the rear bearing cap only. Per the shop manual, you can remove the top bearing without dissembling the engine. I don't know if you can buy just one double-groove bearing but the rear bearing is the only one prone to leaks from what I understand.


It’s the rear seal that leaks and the double grove upgraded bearing and the bearing  cap cut is to reduce oil  pressure on that seal 

A big part of the problem I have learned  is that the original national brand RMS was a more substantial seal but at this point in time only the Best Gasket Rms is available to the best of my knowledge  and causing the problem 

The 65 Serviceman’s publication also addressed a change in the RMS in that year but of no value to us now 


Is there another page to the 65 Serviceman article? I saw the mention of the oil pan rear seal which is not the same thing as the rear main bearing seal.

With this info now available it SB the way you need to go 

If Cadillac think so —- so do I 


You might be the first to install a new set of  crank bearings that would hopefully have the rear bearing with the double grove in it as it is a Cadillac  upgrade redesign of that bearing since 1965 year for that 429 

To the best of my knowledge you are the first to do this repair with the current info on the subject available since I found this info in  a 65 429 Service manual update that no one on this site knew existed 

Everones  Best Gasket rear main seal leaks the best case being just a little after an engine cool down after use 

I would think since  the 65  Serviceman’s publication ——that all replacement bearing would now be having two groves in the rear crank bearing  and the rear cap cut to the 65 specs 
So looking forward to find out your results once your engine is built and installed in your car which  I am sure will be a while 

When someone installs the BG seal with the new shims he will send you if you call them I am again wanting to know the results of that repair 

I think you should do all of the above which should actually fix the rms leak issue in this entire  community 

The final results will be the true test — finger crossed !


Why does the picture that Matti posted of his rear main single slot bearing have two holes in the bottom of the bearing grove—- while Kim’s picture of his double grove rear crank bearing update  has  no oil return holes in it ? 



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