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O-ring crankcase

hgerhardt

Well Known Member
So I'm reading through the latest Kitplanes and see the article on O-ringing the crankcase on the parting line. Fantastic idea, I thought. Modern automotive engines have been doing that for years. It's not an earth-shattering improvement to our (leaky) dinosaurs, but every bit helps to lessen the day-to-day annoyances these things produce.

Now, before I pounce on LyCon (the folks outlined in the story) to have my case machined, what do the other engine builders on this list think about this? In other words, what am I overlooking? The only possible drawback I see is the O ring material shrinking (in length) over the years and causing leaks on the ends, since there's nothing to prevent the O ring from pulling back.

Strange thing is, I thought I keep up with the latest ideas on these subjects, but this is the first time I've ever heard of this being applied to Lycosauri and Contisauri... but I like it!

Heinrich Gerhardt
 
Heinrich, This is nothing new and is outlined in Lycoming Service Instruction 1290E and also for doweled cases in Lycoming SI 1123. This type of repair has been approved bny Lycoming, for a long time. Any crankcase or engine overhauler should be able to help you out.
Good Luck and Happy New Year,
Mahlon
?The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Mahlon, is that the same thing? I thought that SI was about O-rings around through bolts.. this is O-ring material (but not "o-ring" itself) along case split lines (instead of using silk thread)...

PS.. don't have the SI handy so I'm talking from memory.. which is usually not a good thing :)
 
Not at the thru-stud locations...

Mahlon, like Radomir says above, this is about machining a groove in the outer case split flanges and replaces the silk thread and/or any other sealant that could be used here.
 
So, no other engine shops have an opinion on this procedure? On the face of it, seems like one of the better ideas for Lycominentals lately.

Heinrich Gerhardt
 
LyCon O-ringed Cases

I have been using LyCon for this service for several years on 4 cylinder Lycoming with no leaks at all ! You need to torque the cases together then trim the excess o-ring material flush before installing the front main seal or you will get a dribble around the outside of the main seal. It eats up the best part of a thousand bucks but for my personal engines I wouldn’t be without it. The seal remains flexible so as the case moves minutely over time it proves to be leak free.
 
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FWIW, I have 500 hrs on a Ly-Con IO-360 with 10:1 pistons and the O-ringed crankcase. Engine is 8 years old and doesn't drip one drop of oil.
 
Since I posted this question in 2008, I ended up using Loctite 518 when I rebuilt my IO-360 in early 2008, which was 10-1/2 years and 660 hours ago and the crankcase parting line is still dry.

In the meantime I've had to replace intake gaskets at least twice and am therefore very tempted to use Ross' O-ring mod. I say tempted because I'm too busy/lazy to cut my tubes and re-weld.
 
Since I posted this question in 2008, I ended up using Loctite 518 when I rebuilt my IO-360 in early 2008, which was 10-1/2 years and 660 hours ago and the crankcase parting line is still dry.

In the meantime I've had to replace intake gaskets at least twice and am therefore very tempted to use Ross' O-ring mod. I say tempted because I'm too busy/lazy to cut my tubes and re-weld.

Did you use the 518 without the silk thread? I am assuming so as the approved method from Lycoming calls out for not using the tread with the Loctite.
 
My ECI was put together with Hylomar and silk thread, 0 leakage after 15 yrs and 1500 hrs. We used to use Hylomar on some of the jet engine gaskets at the airline so I came to trust it.
 
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