I am going to replace the Rear Main Seal on my 292. Using Neoprene Seal. I seem to recall a couple of People here have used a Sealant like Ultra Black or "Right Stuff" to fill the Side Seal Area and not used Side Seals at all. Any Opinions on this. I read somewhere that its not actually the Crank Seal that Leaks in many Cases but the Side Seals. Ted-any thoughts about this Idea?

  

Mark, while you're there, check the rear main bearing.  If it is worn excessively, the seal is more likely to leak.

John - "The Hoosier Hurricane"

I’m familiar with the practice of using RTV for the side seals but have not done that myself.  Those instances where I’ve heard that being performed was done so while the engine was on an engine stand and upside down.  Doing the side seals with RTV with the engine in the chassis could be a challenge.
 
I use the Best Gasket rear seal kits almost exclusively on the Y engines and do not use the Fel-Pro side seals.  Even on the Ford FE engines, the Fel-Pro side seals are a challenge.  The Fel-Pro side seals are ‘thicker’ which gives difficulty in getting the side seals pushed all the way down into the grooves

Lorena, Texas (South of Waco)

Get a can of 'FlexShot'. Menards sells it. Check it out, it's neoprene rubber, adheres well, high temp. (can withstand temperatures from -76°F to 350°F.), resists fuel better than RTV, comes in a pressurized can with a tip that will get all the way into the side seal void. (I don't own any stock etc. etc.)
I used Ultra Black when I changed a leaking main seal on my 312, engine in place, gravity was not a factor. As I said, if I have to do another one, I'd use F.S. after having tested it on other projects.
Those side seals are a real pain to install correctly and a Mickey Mouse design to begin with!
I believe Ford would have used one of these modern products for the purpose if they were available back in the day. Best wishes.


"FREE SAMPLE"

I have a NOS seal retainer for a 239/256 engine that has a rubber side seal that also circles the retainers bolts.  It is a one year only part and is made of iron like the mains.  I don't know why Ford didn't continue making this part other than cost.  The iron piece part number is EBU-6335-B.  This retainer looks to be perfect for side sealing as well as for the surface mating to the block.  No RTV needed.  Best Gaskets and Felpro make seals for this retainer.  I sure Ted has seen this retainer and would know of any issues for it's use.

ive used it a couple of times and no leaks.ted is right about the fel pro side seals.the last time i used them it took me half an hour and by that time any sealant you put on the bottom was more or less gone.

Genuinerod Posted -

"I have a NOS seal retainer for a 239/256 engine that has a rubber side seal that also circles the retainers bolts.  It is a one year only part and is made of iron like the mains.  I don't know why Ford didn't continue making this part other than cost."

I wonder if the seal was made for the early DIF engines (239/256) rather than the CLV?



So much early info was deleted from the 49/59 MPC that early engine info is difficult to come across.

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Flex Seal is not meant to be used in Situations where Temperature gets higher than 200 Degrees if even that. Meant for more Household Repairs. Just did some research online. Nice Idea but it would melt at Engine Temperature. I think "Right Stuff" is a much better Bet. Designed for Automotive use and will stand up to high Temperature. "Ultra Black" as You have already used looks like it works also. I am going to go with this "Sealant"  Idea instead of Seals and see how it works out. From what I have found from the few who have gone this way it seems to have a good success Rate. As Someone else noted if the Products that are around Today were available when these Engines were new I think Ford would have used them? Still looking for anyone's Input to my Question.



  

Thanks for the Suggestion John. I have some Plastigage somewhere from when I did an Engine 10 Years ago. I would really like to do this Repair this Time and get no Leaks. Looking for Anyone's Input who want's to Offer it.

  

What Sealant did You use that worked?