Rear main seal options

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Old June 14th, 2018, 06:25 AM
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Rear main seal options

I saw a post where using a Ford 460 neoprene rear oil seal had been used on a big block Olds. I was wondering if others had had good luck using this seal? Thanks
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Old June 14th, 2018, 06:37 AM
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Yes. That seal has been used on Olds tall deck motors in place of the rope seal for years!
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Old March 7th, 2022, 06:38 PM
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Would this also work on a 69 350
do I need to pull the crank out or will it go in with crankshaft installed. I'm doing this engine this Saturday I'll be yanking it from the car to reseal and paint
Thanks
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Old March 7th, 2022, 06:41 PM
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The BBO uses the 460 seal. The SBO uses the 292 seal.
The correct FelPro seal for an SBO (BS6141) is under $14 at RockAuto.

Also use the 350 diesel oil pan gasket (FelPro OS30471C) - it's cork with metal core.
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Old March 7th, 2022, 06:47 PM
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Originally Posted by v8al
The BBO uses the 460 seal. The SBO uses the 292 seal.
The correct FelPro seal for an SBO (BS6141) is under $14 at RockAuto.

Also use the 350 diesel oil pan gasket (FelPro OS30471C) - it's cork with metal core.
Awesome thanks man
Will I be able to install the real main with crank in place do you know
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Old March 7th, 2022, 06:54 PM
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You have two problems
  1. Removing the old main seal
  2. Installing the new main seal
Each one of these is a challenge in it's own right.

The CSM has a procedure for removal and replacement of the rear main seal while the engine is in the vehicle.
I don't know anyone who has ever tried it. Maybe someone else can chime in.
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Old March 7th, 2022, 07:03 PM
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Originally Posted by v8al
You have two problems
  1. Removing the old main seal
  2. Installing the new main seal
Each one of these is a challenge in it's own right.

The CSM has a procedure for removal and replacement of the rear main seal while the engine is in the vehicle.
I don't know anyone who has ever tried it. Maybe someone else can chime in.
Thank you
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Old March 7th, 2022, 09:28 PM
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I've done the in car replacement method a few times that used a special tool to pack the upper seal tighter using short pieces of a new rope seal and replacing the entire lower half rope seal. It worked well but I wouldn't recommend this method because of the special tool required and the age of the old upper seal. The tool could be made, it is just a punch with and end about 3/8"? which mimics the shape and radius of the rear main seal groove in the block. You put the tool in the groove, tap it to pack the upper seal tighter and then cut a piece off the new seal and pack it into the groove where the original rope remains but has been compressed a little.

The neoprene would be a superior repair.

Good luck!!!
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Old March 8th, 2022, 07:50 AM
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According to what you may read in various places, if you can get the old rope seal upper half out, you should be able to slide the new rubber replacement seal into place! I personally have never tried replacing the seal without removing the crankshaft. Let us know how it works out for you.
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Old March 8th, 2022, 08:04 AM
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Originally Posted by 67OAI
According to what you may read in various places, if you can get the old rope seal upper half out, you should be able to slide the new rubber replacement seal into place! I personally have never tried replacing the seal without removing the crankshaft. Let us know how it works out for you.
Ok I will if we end up going that route
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Old March 8th, 2022, 09:43 AM
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when i did the 455 seal for my 76 i removed the rear bearing and only loosened the rest enough to raise the crank up enough to get the old seal out and the new one slid in pretty easily .retorqued all the bearings and was good to go didnt have to mess with the rod bearings at all.Of course this was with the motor on a stand i would not attempt it in the car laying on my back (those days are over).
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Old March 8th, 2022, 09:49 AM
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Have never done the neoprene on the Olds but definitely would. SBC neoprene uppers are routinely replaced with the engine in the car, should be able to do it on an Olds but again I haven't tried.
Good luck!!!
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Old March 9th, 2022, 03:45 AM
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Originally Posted by deadeyejedi
when i did the 455 seal for my 76 i removed the rear bearing and only loosened the rest enough to raise the crank up enough to get the old seal out and the new one slid in pretty easily .retorqued all the bearings and was good to go didnt have to mess with the rod bearings at all.Of course this was with the motor on a stand i would not attempt it in the car laying on my back (those days are over).
They 292 slides in very easy if coated in oil. The AMC 6 seal is more of a challenge, definitely tighter. It is what I am using on my 358 build. Make sure the groove in the seal is towards the crankcase. Loosening all the mains is pretty much necessary unless the rope seal was done recently. My 73 350 had all the gaskets including a rope seal, it took 5 minutes to remove and replace with a 292 seal. I ironically saw an old 292 rope seal removed in a old Ford truck. Many hours of fighting for that particular mechanic in our shop. Expect many hours and the proper tool would help a lot for in car removal of the rope seal.

Last edited by olds 307 and 403; March 9th, 2022 at 03:49 AM.
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Old March 9th, 2022, 06:16 AM
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[QUOTE=olds 307 and 403;1411449]They 292 slides in very easy if coated in oil. The AMC 6 seal is more of a challenge, definitely tighter. It is what I am using on my 358 build. Make sure the groove in the seal is towards the crankcase. Loosening all the mains is pretty much necessary unless the rope seal was done recently. My 73 350 had all the gaskets including a rope seal, it took 5 minutes to remove and replace with a 292 seal. I ironically saw an old 292 rope seal removed in a old Ford truck. Many hours of fighting for that particular mechanic in our shop. Expect many hours and the proper tool would help a lot for in car removal of the rope seal.[/QUOTE
Thanks I got both seal and pan gasket yesterday along with odds and ends Saturday morning the plan is to remove engine and transmission.
i will have motor on a stand. Anyone know off hand the torque spec on the main caps? I'm just going to unloosen the bolts just enough for a quick inspection and proper install plus making it an easier task.
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Old March 9th, 2022, 08:18 AM
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Check the posted "sticky" at the very beginning of this forum (Big Blocks) for most all Oldsmobile engine torque specs.
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Old March 9th, 2022, 09:01 AM
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Have fine crocus cloth available to clean/polish the sealing surface if needed. Work clean to keep all abrasives and grit from polishing out of the engine.

Since you are in that deep, how is the timing chain...MAW's ? ? ?

Good luck!!!
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Old March 9th, 2022, 01:42 PM
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Originally Posted by Sugar Bear
Have fine crocus cloth available to clean/polish the sealing surface if needed. Work clean to keep all abrasives and grit from polishing out of the engine.

Since you are in that deep, how is the timing chain...MAW's ? ? ?

Good luck!!!
thanks I will I have no idea what the condition of engine is my uncle just bought this monster all I know is it runs
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Old March 14th, 2022, 11:26 AM
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Well we removed engine and trans set the engine on a stand and started the tear down it seems like this motor was rebuilt probably not long ago as there was no sludge or build up anywhere I removed the oil pump and rear main cap and was able to remove the rope seal with needle nose pliers and installed the newer seal by soaking up everything with oil and slightly pushing it in we'll see what happens when she fires up hopefully no leaks here are some pictures


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Old August 21st, 2023, 07:50 PM
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Originally Posted by v8al
You have two problems
  1. Removing the old main seal
  2. Installing the new main seal
Each one of these is a challenge in it's own right.

The CSM has a procedure for removal and replacement of the rear main seal while the engine is in the vehicle.
I don't know anyone who has ever tried it. Maybe someone else can chime in.
I'm doing one right now and found out if you use a felpro viton seal you do not want to shave the outside like some videos are showing because it will make the seal too loose and sloppy. I just ordered another seal and going to retry without shaving the outside of it. Another post said that if you use the Viton seal that you did not need to shave it. If you order the $30 Felpro Ford rear main seal from Summit it is a Viton seal and don't need to shave it..I was able to get the shaved one in just fine but maybe a little more difficult with it not shaved. One person posted to loosen up the other crank bearing caps which I may try if the other one doesn't feed in there. Also need to shave off that little square tab on both seals for it to seat properly.
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