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Felt Rear Main Seal


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After looking high and low for some concrete information on the subject of felt rear main seals I was able to get this from Fel-Pro gasket regarding the issue.  I know you guys have loads of personal experience which I fully respect but what I was looking for was some sort of manufacturing based guideline on how to approach this.  This is just to share what they had to say on the matter and to put it out there for you folks to evaluate if ever faced with the circumstance.  

Hi Brian,

After some searching (we don't have a service manual for this application on-hand) we have determined it would be best to treat this seal like a rope RMB seal. 

Install the RMB seal into the block after soaking it in oil. Rope seals have graphite in them for lubricity while felt does not, so that’s why we suggest soaking the felt in oil. Install the seal into the block cavity first and use a large socket (3/4” or larger) to roll the seal into the groove. Install the crankshaft & carefully trim the seal so it sticks up past the block edge about 1/16”. Install the RMB seal into the RMB cap in the same fashion. Since the felt is oil soaked, no RTV can be applied to the ends of the seal as it will not cure properly. We would apply a thin coat of RTV along the sides of the RMB cap where it joins the block to seal it. Like a rope seal, this type of seal will likely seep some over time.

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