Hi all!

Hope you are al doing fine.

My real main seal leaked so i pulled the engine. While the engine was out and the oil pan of i took the opportunity to look at my main bearings. They look fine accept for some initial break in marks because of Iron filings from al the new components (lifters, camshaft, rockers Etc. Etc.)

I ordered new bearings (sealed power from Rockauto). Now bear with me... These mains have 2 same size bearings for cap 2 and 4. For cap 3 there is a bearing with thrust plates. So that is the easy part. Now for cap 1 (front of engine). And cap 5 ( back of engine with the main seal). There is two options. One set of bearings has two oil grooves and the other set is wider than number 2 and 4.. Does anyone know which bearing goes on front and back?

I kind off remember reading somewhere that the grooved one goes on the back but now i'm not sure anymore. 

Thank you for the help. 

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You should have your answer shortly as the boys check in 


Can we get this fellow an answer to his crank bearing Question —-pls ?

Jeroen there is a good number of threads in the search engine on the top  right of the home page in regards to the rear cranks seal that should give you some tips on the installation and  best brand seal to be using etc 

At best  when installed correctly the seal will leak a bit only when the car sits and cools down after being driven with no signs of any leaking at any other time  ( expansion and contraction of the seal ? ) 

I have found that a conventional oil ( 10w - 30 Castro’s with a ZZDP Rislone additive ) leaks a bit less than the Syn oil I have mostly used in the past until the Syn oil ( mobile one ) could no longer be used with a flat tappet cam due to a chemical change ( reduction in protection ) to the product for newer car application 


Most engine oil off the shelf cannot be used with our flat tappet cams in our  Iconic Classic Antique Cadillacs 


I have been searching the great and mighty internet and even better this website. I got my answer from another cadillac website the bearing with extra oil grooves goes on the back of the engine. I used a Best Gasket oil seal because they seem to do the job better than other brands. I installed the seal 3/8 of an inch out so de halfs don't line up where the cap meets the block. Used a little dap of sealant on the seal end halfs. The oil i'm currently using is a 10/40 lucas classic oil and i use a zink additive to protect the camshaft.

Thank you! 

Let us  know how things go. It has been 8 years out since I rebuilt mine and don't remember issues with the main bearings... but again it has been 8 years. I did offset my rear seal and it still drip leaks a bit when the engine has sat cold for a while and the seal shrinks a bit. Reading your question makes me wonder if I installed my right! LOL I just can't remember running into an issue. My biggest heartburn was getting those oil rings on the pistons and inserted correctly.

Oh no it was not my intention to make you doubt haha. 

The bearings look like this:

Bottom pair is for cap number 5 and top pair is for cap number 1. I only have some trouble with the endplay at this moment. Endplay is to small. Will have to sand down the thrust plates. 

So far als the oil rings issue... I think i learned many new curse words when installing those... 

Best Gaskets —is the  rear seal of choice for the crank from prior posts on the subject 

Important to follow drying instructions on the sealant of choice used before moving forward 

There is a sealant that I do not recall the name of that cures without air required to be present which might be a good one to use on the rear seal 

I do see you have your engine lubrication under control and correct for our cams 



I did indeed got a sealant that cures without air. The best gasket oil seal is a way tighter fit than the one that came with the engine rebuild set. I used some engine assembly lube on the back of the seal so it would slide in better. Did not use sealant on the back of the seals or in the block or cap. I did make some sort of dam with loctite 648 glue/sealant where the cap meets the block. A little of the stuff goed a long way because of those machined surface. When tightening the bearing cap the seal halfs really get crushed into each other. I did my best to offset the seal halfs exactly the same but because of the tight fit it is hard to do. Hope it al went well. 


I think I would use the sealant on the face of the end cap matting surfaces myself to prevent possible seepage at that juncture and glue ( using sealant ) the seal to the rear crank cap in as many places as is possible —to the rubber seal ( the seal groves etc ) and let that cure per instructions 
Much more of an option  to do that with the engine out as opposed to doing the job  with the engine in the car ( which is possible ) 

The manual does not show any offset of the rear main seal from the end cap jointing surfaces ( Cap joint meets the seal joint head on )  but it does seem to be a good idea and make good sense to do an offset 


This community is still  looking for the perfect fix when replacing the rear crank oil seal to be preventing any oil seepage even when the engine cools down which is now the norm on this site  ( Jason and myself included ) 

Not sure at this point after a number of repair threads that it is possible to  do any better than some slight leaking when the engine is cooling down when parked ( engine cooling down takes a good while with these engines holding heat a long time ) 

My oil loss is very mineable ( a little motor oil always looks like a lot on the floor ) In the pan I keep under the engine and again less with the conventional oil I have gone back to to be keeping my oil viscosity at the desirable 10w - 30 with zinc additive the stock engine calls for 

Glad to know the — Best Gasket -  gasket looks to be a  physically better replacement seal than others you have visually seen which supports other threads on the subject here 

Good idea to be using the lube you did on the seals sliding surfaces to prevent any friction from distorting the seal during a break in seating procedure at start up time although the seal SB submerged in crankcase oil or subject to oil in the crank bearing from oil pressure there at start up 

Much good luck with your bearing and seal replacement repair 

We are all interested in your results as this is an ongoing issue for many of our community 


Do you fill the oil pump and oil filter and prime the engine  before a start up —turning the distributor shaft ( dist removed ) to circulate oil thru out the internal engine before staring the engine ?



I will keep you updated on how things work out. It is going to take a while to get the engine and transmission back in (transmission is rebuild with new torque converter) wonder how much power i will gain. The weather isn't being nice to me this summer. Since i do everything outside with no car lift it wil take some weekends to install everything. I use a electric drill with a 12mm socket that fits the shaft on the oil pump. I also put a oil pressure meter in the engine to see if oil pressure stays good on start up.

Start up this time will be interesting. I have a new throttle plate (holley) and a impco 425 propane (Lpg) system. Hope it goes as easy as coocking on gas (pun intended) haha.

Thank you! 

Love to know more about running a Cadillac engine on propane and what that is about 

When you put  the car back together do fill us in about what that system is doing for you regarding performance etc 




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