My 292 is at the machine shop. The block has been bored, decks milled and the mains align honed. I should have it back in a week or so and will begin assembly.   It's been years since I worked on a Y Block engine.  I always remembered them to have leaky real seals.  My engine had a rope seal when I disassembled it.  This seems like ancient technology to me.  I have read many Internet articles on installing a neoprene seal.  Sounds similar to all the big blocks I have worked on.   Do the new seals leak?  Why would anyone install a rope seal in 2018?

Did U read the Article that Ted Authored?  Something I read somewhere is that it's not the actual Seal that Leaks but the Side Seals. One Solution to side Seal Leaks is to fill that area with a Sealant instead of using the usual Side Seals.Of course this can only be done with the Engine out and upside down on an Engine Stand. 

  

I've built two Y blocks in the past three years and used the neoprene seals with good results. The rope seals made today are different material then the ones of the old days so I avoid them..

If you can find an old school 50s or 60s NOS rope seal I bet it would work fine ancient tech &c. regardless. They were made with better materials. Soak it in oil for a couple days before assembly.

Ted Eaton has a super helpful article on how to setup a neoprene seal and tech tips on "doing it right doing it once".

http://www.eatonbalancing.com/2008/09/10/neoprene-rear-seal-installation-for-the-y-and-others/

https://www.hotrod.com/articles/0810sr-bestgasket-rope-seals-ford-y-block/

I did read Ted's article.  Good information.  I assume if the crank is round and the neoprene seal is new, the seal itself won't leak.  As I recall the side seals don't just slide right in and can be somewhat difficult to seat and the nails have to be driven to one side.   I remember the part about offsetting the seal ends.  There is mention of a problem where the neoprene crank seals don't fit all the way into the grove.  How common is this?