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Front Crankshaft Oil Seal


Matt Wilson

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I'm looking at the front main seal that will go into my 25" engine.  It's from a Best Gasket kit.  It doesn't look like the original or like the image shown in a couple of my repair manuals.

 

The first image below is from one of my manuals and it shows not only the seal, but also an oil seal gasket.  When I took apart my engine, I'm fairly certain it didn't have this gasket, and my new gasket/seal kit from Best does not have this gasket, as far as I can tell.

 

Also, the new seal doesn't look like the old one, nor does it look like the one in the manual.  It's the correct size (inner and outer diameters and thickness), but looks a lot simpler than the one in the manual.  You can see the differences between the original seal and the new seal in the next few photos.

 

So do I just smear a little sealant on the O.D. of the new seal, and maybe even the front face, and then press it into place in the timing cover housing?  Or do I need to find (or make) the seal gasket shown?  Also, is it an issue that the new seal looks so much simpler than the one in the manual?

 

Thanks.

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Edited by Matt Wilson
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I've never seen a separate gasket on any front cover seal on any motor I've built. Install your new seal and put your cover on. A little oil on the outside and inside rubber lip and you should be good to go. 

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The outer housing of the seal usually contains a sealant as the coating. notice how the blue doesn't cover the entire metal part.  Call Best and ask them.

 

As for the actual seal itself, the old one was a leather ring, essentially.  Which is why your manual shows it being square cut.  Modern seals use nitrile (usually) and it's a lip seal.  The lip is cut and installed in such a manner that if crankcase pressure increases it tends to force the lip tighter onto the crank.  Whereas the old square cut leather seals would leak by.  Another change is the radial spring used to apply even pressure on the lip seal to maintain even contact on the crank.  Leather, being a natural product, is not consistent in it's composition so you may have issues with even contact there.

 

Here's a pretty decent, but generic, write up on them.

 

https://www.machinerylubrication.com/Read/30391/lip-seals-importance

 

SKF installation instructions  

 

 

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16 hours ago, Sniper said:

The outer housing of the seal usually contains a sealant as the coating. notice how the blue doesn't cover the entire metal part.  Call Best and ask them.

 

As for the actual seal itself, the old one was a leather ring, essentially.  Which is why your manual shows it being square cut.  Modern seals use nitrile (usually) and it's a lip seal.  The lip is cut and installed in such a manner that if crankcase pressure increases it tends to force the lip tighter onto the crank.  Whereas the old square cut leather seals would leak by.  Another change is the radial spring used to apply even pressure on the lip seal to maintain even contact on the crank.  Leather, being a natural product, is not consistent in it's composition so you may have issues with even contact there.

 

Here's a pretty decent, but generic, write up on them.

 

https://www.machinerylubrication.com/Read/30391/lip-seals-importance

 

SKF installation instructions  

 

 

Thanks.  The seal I removed from the engine was rubber or maybe nitrile or neoprene, rather than leather, and it had the cut lip and spring and all.   The engine was from an early 60s Power Wagon, and either they were using somewhat modern materials by then or the seal had been replaced.  But yes, the seal pictured in the manual may very well have been leather.  Good point about calling Best Gasket.

Edited by Matt Wilson
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5 hours ago, DJK said:

Speedi sleeve may be needed on the hub if surface is grooved, also be sure to center cover on hub before tightening down.

Thanks, yes, I've already installed a Speedi-Sleeve.  It was definitely needed.  With my old 230, I thought I had centered the timing cover over the hub pretty well, but I must not have, as that thing leaked like a sieve.  I hope this one goes better.

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