Aluminum /6 Rear Main Seal

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62 Signet

62 Signet
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I am rebuilding an aluminum /6 225 and am trying to figure out the rear main seal installation. I have a Felpro neoprene 2-piece seal which is simple to install. What is confusing me is the (removable) upper seal retainer has a smooth outer surface while the mating surface of the block has a small groove in it. It appears like a seal would go there but none was included in the kit. Does anyone have any experience with this? Would I be safe just putting a bead of silicone or RTV sealer in it? Also, the same retainer has a recess on each end similar to the bottom seal retainer where the "L" shaped side seals go. Does a seal go there or should I just put silicone or RTV in it as well? Any help would be appreciated.
 

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That rear main seal looks a bit smaller in width than the cast iron block version. It may be that seal is unique to the aluminum block. Silicone won't act as a good seal on a moving part. You may have to find an old school rope seal that you can cut to fit. A dab of RTV where it meets the end seals and pan gasket would be the only thing I'd use.
I'm not real sure what you mean by "uppper seal retainer". The upper half of the main seal should fit into a groove in the block. The lower seal half fits into a groove in the bolt-on seal retainer. The ends (right and left sides) of the retainer have a seal also where it meets the block. There again add a little RTV to the ends of the seals.
 
Thanks for the reply. I believe you misunderstood my problem. I don't have an issue with installing the rear main seal, only with installing the upper seal retainer. With the aluminum block, both rear main seal retainers are removable, an upper and a lower. The second picture shown is the upper. The first picture is the block showing where the upper seal retainer goes. Note the groove in the top picture and then look at the corresponding back of the retainer. I would think the groove is there for a purpose but there is no corresponding lip or groove on the back of the retainer. This is where I was thinking putting silicone or RTV (in the groove). Also, the ends of the retainer have recesses similar to the bottom retainer (that does hold a seal). Even though the upper retainer fits snugly against the block, it doesn't appear to use any type of seal. This is where I'm wondering if I should use some RTV to make sure I don't develop seapage at this connection.
 
There is a REALLY nice write-up in the articles section of slantsix.org. You are going from the rope style to the rubber style. RTV will work fine but really isnt necessary where your worried about.
Frank
 
You're correct: there are additional pieces in the aluminum-block rear main seal kit not needed (therefore not present) in the iron-block kit. You'll have to find these pieces from a gasket specialist (Hemmings lists several who have hooked me up before) or goop it with RTV and hope for the best.

Also, you know you need the special aluminum-engine head gasket, right?
 
Thanks Dan for the advise. I went ahead and installed the upper seal retainer using RTV. I think I got a good bond. I did order the newer 2 piece rubber seals and installed them. Also, I was able to find a NOS copper head gasket.
 
Mitchell Motor Parts (706-337-4606). They might have changed their name recently but I think the number is still good. Slow service but a large selection of NOS parts.
 
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