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Crankcase O-Ring Groove Mod

Low Pass

Well Known Member
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Anyone have experience with having an o-ring groove cut in their crankcase split line flange lately? Haven't heard much about this mod in the last 8-10 years. Would you do it again?

Correction - Div-Co does not do this. Ly-Con does...

I understand the downside - one-way mod, removes material from the crankcase flange...

Any actual experience and observations would be much appreciated, as I have a case being worked currently. Note - I'm looking for actual experience - good and bad - with a possible improvement modification so I can personally determine if the cost is worth the benefit. Not opinions on why it shouldn't be done.

Thanks!
 
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I have seen case leaks on Lycomings but have seen more without case leaks. IF the case is sealed in accordance with Lycoming recommendations, the odds are that it will not leak.

To me, it sounds like a fix looking for a problem.
 
IIRC that modification was created and a STC obtained by Lycon in Visalia, CA.

If that is the case, while it maybe a "fix", it has a very good pedigree. :)

A call to Lycon might give you the background and more information. They are very "RV-friendly".
 
I think Lycon has a patent on the mod, plus the CNC equipment. Pretty sure Nicksons can’t do it.
Tim Andres
 
Oh Contraire Mon Ami.. Lycoming SI 1290 for body fit thru stud cases and Si 1190 for doweled bearing saddles allows it and tells how to do it. It is done a bit differently than the way some do it but many of the case remanufacturers have their own approvals. But if they don't, the instructions and approval is there from Lycoming for any one to do it.
Good Luck,
Mahlon
 
Crankcase Seal

It appears that Lycoming SI 1290 relates to sealing existing leaks around case studs or dowels, but not sealing around the entire case split line as a proactive action.

That is what LyCon's process is designed to do - solve the problem around the whole case perimeter before it possibly becomes a point problem later in the engine's operating life.

Am I missing something about SI 1290 I didn't understand?

HFS
 
Yeah I think we?ve split off into two discussion now. The perimeter O ring mod Lycon does, per the original post, and the O ring mod around the studs per SI 1290
Tim Andres
 
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