Looking for help here from the expert rebuilders.  I just put the engine back in after the re-build and used silicone on the front cover oil passage instead of the o-ring and nylon.... 

 

I seem to remember having done that last time, and it worked fine.  I think I did it last time for some sort of good reason, but now I cant think of any good reason not to use the o-ring.  Then in the middle of the night I realized that the oil pressure there is probably quite high, and that is mostly a big gap to fill....

 

Do any of you experts use silicone there instead of an o-ring?

--
David Leonard

 

No.

 

That junction has killed hundreds of rotaries. The high oil pressure and a very flexible front housing just allows the housing to flex forward and part of the "O" ring escapes from the boss, and with only part of the "O" ring trapped, holding that junction open, there is little to no oil pressure. You can but in the later (thicker) "O" ring with the nylon back up washer trapped in the junction to keep the "O" ring in place.

 

Or, just install a copper or aluminum ring to replicate the thick "O" ring. It is rigid, so it cannot deform and hold open the junction. It will not deform or blow out. It is cheap and lasts as long as the engine. Make the metal ring stand 1/16" proud of the boss. It doesn't matter if you use a gasket for the cover or not.

 

If you don't like problems like this in an airplane, You can drill out the plug in the end of the lateral gallery that runs under this connection and is the drilling that forms this gallery.

 

Use A boss and "O" ring connection because a tapered pipe fitting will split the thin walled casting.

 

If you go that way, build a disc to fit the problem junction. If you still run the OMP, drill a .020" hole through the center of this disc, so the OMP will be supplied oil.  

 

No amount of sealant will work. You need that "O" ring and backup washer. Or better.

 

Lynn E. Hanover