Hello all , just spent better part of the weekend installing a new rear main seal and pan set on my 63 390 , all though it slowed the leak down considerably , l still have a drip , l used a Felpro seal , l did not put it in backwards and cleaned and torqued everything, is there a brand that is better then what l used ? , any input would be appreciated, thanks .

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Did you compare the new seal to the old seal?  Last time I checked a few years ago, Felpro had the wrong seal. They had the 62 and earlier seal as the same for the 63 and up.  The 62 seal is smaller and leaves a gap between the halves. 

Best Gasket has the correct seal. I have put in a few, and a few drops of oil is to be expected. 

thanks for the reply , yes l  did compare the two , looked identical , when you say a few drops is expected are you talking dime size spot on the ground over night ? 


Have you had any additional feed back on the rear main seal  you installed that had a —one inch seal  off set — off of the center line of the rear main bearing cap joint  ?

That repair might be the first seal install that has not leaked ( at least initially  ) but wondering if you know anything new about how that seal repair is holding up after some additional miles on it 

In almost every case  on this site the most that can be expected is that there will be a small amount of  engine oil leaking from the seal that happens only when you park the car and the engine cools completely off for a long period of time leaving a 6 inch oil spot ( approximate  in a pan under the engine ) but no oil staining when the car is used and out and about ( and engine is at operating temp ) 

A very small amount of engine oil looks like more than it is —when forming a spot in a drip pan or on the ground as it does spread out a lot 

It is manageable if you park over a drip pan and keep an eye on it as the amount of oil has stayed the same and is small and acceptable ( non would be better !) until we find a solution if there is one 

My own oil seal leak  in the  drip pan has been reduced some since I stopped using Mobil Syn motor oil ( for about 30 plus years ) that no longer meets my flat tappet cam needs  ( formula changed ) and have gone back to using a conventional 10w - 30 Castrol motor oil with a  Rislone zddp additive to meet my flat tappet cam needs and be staying with the 10w - 30 weight oil the engine requires 

Some other gasket seal leakage has improved as well going back to the conventional oil which has worked out very well for my  own needs 

We seem to be doing the best we possibly can with some leaking after a rear main seal repair until hopefully something changes for the better in the future to correct the issue 


Tony, my rear main seal started leaking, so I can not claim a drip free rear main seal.  


Thanks for your feedback on your rear  seal repair 

Was hoping you might have  solved the problem for all of us 

Back to the drawing board— as a bit of a leak from this seal looks like something the owners of our year Cadillacs will have to live with 


I think l have figured this out , Russ got it right , Felpro lists that seal from 59 to 62 and no listing till 69 , so my supplier has given me the earlier wrong seal , they are compensating me for seal and pan set , stil out my time and oil , and the fact l hate doing things twice , picking one up from Best gasket tomorrow as well as a pan set , yes Tony it was indexed when l took it apart ,

On the plus side, l installed a petronix ignition, 8mm wires , plugs , cap , rotor , rebuilt the carb , new pvc system, synthetic trans fluid , made all the trans adjustments (tv etc) and lowered the back 5 inches by installing G body springs , looks great and feels like l added 50 hp , thanks for the reply’s , l will add pics and let u know on seal job # 2 , cheers .

Based on the fact that all the rear main seal repairs done on this site over many years  have leaked wether  done with the engine in or out of the car you should evaluate the amount of oil you are loosing from that seal and live with it if you can —if it is a reasonable amount-  and only doing it a second time if it is leaking more than discussed or reasonable 

You can pretty much count on it leaking after your second attempt I am sorry to say being on this site many times daily since 2006 

That is my best suggestion based on following this repair over many years and this repair is no walk in the park ( a hell of a lot of work ) 

The ball is in your court 

I hope I just  may have saved you many hour of labor 


Hey Tony , l’ve been in the automotive, truck and motorcycle repair business as a tech for almost 40 years and one of my pet peeves is oil leaks , l’m assuming you have a 64 , when brought home new do u think the owner of his brand new Cadillac had a spot of oil on his driveway the next morning? Probably not , that’s what lm going for ! Will let u know when l get around to redoing it , thanks , Cheers!


My 64 convert came home off the showroom floor  in 64 and there was no sign of any oil on the floor  for many years so you sure do have a point there 
Hoping your knowledge and experience will help to resolve the  main rear seal leak issue and be helpful for many in this community 

I am only letting you know the results of the half a dozen or so attempts to solve the problem with no positive results that were posted on this site including your attempt 

Some have indicated the wear factor regarding the condition of the crank cap bearings and any slack there may be a factor in the rear main seal getting damaged and  leaking or being damaged by that movement 

Then again Jason Edge who is maticulas at all he does ( and our Web Master ) rebuilt his entire engine ( all details posted on this site )  so all is brand new regarding his cranks condition still has the same rear main seal leaking as explained thru out this thread 

Thank you very much for what you  have added to this discussion and look foward to your future results due to your background 

We need more men with your  kind of background experience on our site 

I do understand your feelings about oil leaks 

Looking foward to hearing back from you in the future regarding the seal repair 





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