Per Tony,  i am starting a new thread on my adventures with this rear main leak,

i posted a video on a 390 engine of a rear main seal replacement but the engine was out of the car,, gave some insight as to sealing and materials etc.

One of my neighbors has a hoist,(yeah!) and has allowed me to use it,, makes it a lot easier than rolling around on the asphalt in the street and is enough higher that its not too confining under there.  I did have to pay attention to the lift points though as it seems you cant just put those lift arms wherever you want..

As of this evening, I have taken the exhaust loose, the steering loose, and the starter is out,, took about 4 hours to do that.  I guess there is nothing earthshaking to report on any of this.  Tomorrow, I will take the pan off and proceed from there.

To be clear before proceeding.

the 63 manual says to insert the bearings in there slots, do not pull off wax coating as that will aid in insertion.  I do not see any wax on my gasket, so my guess they had it on the old ones.,, 

Now, the question here is,, do i add a touch of oil or something to aid in that insertion process,, the manual does not suggest it, as i describe above, or, just insert dry, as is..

it does say apply rubber cement to cap and block mating surfaces, and gasket ends, but that is the only reference in the 63 manual regarding lubricaitng the seal for installation,,  so is that correct?? insert dry??

the you tube video says to use lubridation after insertion so it wont be dry on start up, so i plan to do that as well.

i will try to take a few photographs of things once i get the pan off,  i m sure most have seen the underside, but its my first venture in there and post them for reference.

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OK, i had to check with Shane on this, because I couldn't recall what we/he did.

I've stayed out of this a bit, as I have an issue with some advice that has been given from time to time. No, i will not go any further on that point.

With Kim's rear main, it hasn't been done all that well/neatly.

You need to grind a drain into the cap, to take some pressure off the rear main seal. Mine was done very neatly, as Shane who did it, is a bit OCD from time to time.    understatement right there.

If done correctly, the drain will look factory.... Kim's is a little bit rough, but that's ok, it will still work ok.

Consider, the amount of oil that gets up against the seal is quite high, any draining of that oil back to the sump/pan and away from the seal is very desirable. 

Just a little bit more from Shane.....

There's nowhere for the oil to drain away from rear crank journal before seal. So if oil pressure is 35 psi, that pressure is on the seal.

  • Kevin,  i hv no idea who put those cuts in that cap.  But to my untrained eye,  i could tell it looked like a mess,  your dealing w a rank amateur here, so if u hv a suggestion.  Let me kno.  Anything to reduce this down.  

This might be making some sense  now why someone took a chop saw to Kim’s rear seal cap as that would be increasing the  oils path back to the oil sump and reducing pressure on that seal 

Although no excuse for how messy  that cut was done in Kim case by someone 

Things that make you go——Hummmmmmmmmm !


As Mark explained earlier  here the open grove between the crank bearing and the seal on the lower rear cap is the oil path back to the oil sump for that bearing 

Making it wider would increase oil flow and reduce oil pressure 


The oil coming out of the side of the last crank journal is basically slamming into that rear seal ( at  35 lbs ) 

 before it drops into the oil pan and the only  side of a journal  that has this issue 

This discussion about reducing pressure in that location is very interesting ——

I think that Kevin and his boy Shane should take a bow myself 


I looked at a 64 end cap, and it does have that oil drain. I don't have my lap top right now to verify part numbers, but the drain is build into the 64 block. I checked 2 blocks.

The long cut on the back belongs there, the cuts on the face of the cap do not.

this thread is badly over-responded, so no one will read this advice, but never ever do this, all future main seal changers!

The rib in the main cap was  not just there for looks, it was there to create a well to hold a small amount of oil to lubricate the main seal.  The oil is supposed to puddle there, and as the crankshaft spins, the turbulence of the air around the crank pushes the oil up and around and keeps the seal journal consistently covered with a film of oil.   Sometimes people over think things and believe they know better than the engineers who built the engines, and this is a case in point.  

The long slit in the bottom of the cap is there from the factory, in all 429s I've seen, and that handles the pressure issue.  The transverse cuts added by some would be genius actually ruined a very good practical design.  

Dnt be too hard on all the responders,  im the reason for so much extra banter, i hv no idea what im doing, so i hv to ask a lot of  questions,  some may seem stupid, but i do learn from each answer,  hopefully, nxt tome someone does this, it will make some sense,  especially those videos,  ibreserched and watched about 10, after i got help here verbally, then the eyes on video helped it make sense,..somewhat,  

Now, you hv said that my bearing is worn, could the possible  loss of oil from those unauthorized slits hv lead to a faster wear pattern or is it more likely just use.  Overall, the car has 157k miles,  it was rebuilt in 99 or 2000.  

the slits won't wear the bearings, the engine wasn't supposed to last 157,000 miles, 100,000 was a huge milestone for the engines of that era, and usually they run down by then.  It's just old.    
Luckily, the main journals on these engines are like tree trunks, so the clearance being a little over won't usually lead to any adverse symptoms.  These engines never have rod knocks or main squeaks unless they are run completely dry because the bottom end is really overbuilt.  
The crank bearings will cause a loss of pressure, and may be the cause of the oil light delay, but once it's running, it will be fine.  

So where do youbgo at say 200k assuming i get it that far.  Do the blocks get comprimised, orvdo you just rebuild again w all the moving parts?  I like driving these cars. i usecmine quite a bit.  Im just wondering what the future of tan engine and its options are beyond where i am now.  I turn 60 nxt month, so im not gonna be buying green bananas anymore, but just as a general question for these engines.  I had hoped to drive it back to MS in a couplecweeks from MT,  

Kim, First, If the car has 157K miles on it, but the engine was rebuilt in 1999 or 2000 that does not tell me if the the engine has 5K miles on it or 150K miles on it since rebuild. Second, when you rebuild an engine you look at max clearances and if needed, have the crank main and rod bearing journals machined and buy oversized main and rod bearings to match the new machined spec.  When I rebuilt my engine in 2012 the piston cylinders, rod bearing and main bearings were all just under the max clearance, so I had the crank polished and checked for balance, and went with stock bearings and pistons to save the machining and over-boring for another day. This was on an engine with 158K miles so as Mark stated, these cranks are built like a tree trunk. When you get ready to rebuild your engine, your machine shop can spec everything and see what needs to be turned/machined.  You will have a short list list of things like compression tests and vacuum tests you want to do on the engine, unless you just know it is burning oil, and/or is worn out. 

Right now it is my understanding you are just trying to replaced a leaking main seal. I would fire the car up, put some cardboard under where you park the car, and periodically check the leaking, and enjoy it.



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