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C-85 intake valve leaks

mbsyvers

FRIEND
NW Mn
I noticed a thin oily deposit on my carb airbox (7 ac). Found no oil leaks. During 100 hour found #2&4 cylinders to be 65/80 which is down from mid 70’s. I could also hear air escaping through the airbox. Engine still developes full rpm. Any advice before I pull cylinders would be appreciated.
thanks
 
I've never NOT had some oil in my airbox, kind of part of having a slimy little lawnmower engine powering your plane. Compressions are low but not necessarily bad. Run some MMO (marvel mystery oil) in your gas and see if it improves things. Another issue could be lead buildup if you're running avgas full time.

Don't pull the cylinders right away. Bob Turner has been through a ton of small Cont's and will have some sage advice for fixing your issue I'm sure.
 
I am running 100 LL and after problem surfaced i have added mmo at 1 oz per gallon of fuel and 8 oz in the oil.
 
These little engines seem bulletproof. I am running 3/4 auto & 1/4 LL. That gives me the lead content of old 80 octane, and seems to ameliorate exhaust seat problems. I would never admit to using a dollop of MMO at each fueling.

Remember, we do a compression check every single flight. A Mooney gets a compression check once a year. On average, a cylinder goes bad at the six month point.

Also remember - a cylinder can go soft with a piece of junk in a valve seat, and may fix itself the next time out. Shops often yank cylinders prematurely, and on these old engines the cylinder shop will red tag it in a heartbeat.

I have had three cylinders crack over 60 years. I am replacing one today. Even with the crack, it developed full power. We watched it for two weeks before I hooked the air to it to see what was going on.

A small Continental will run forever with care - or you can pull it apart and spend $20 grand - your choice. I have had excellent luck over 6000 hours behind these things.
 
These little engines seem bulletproof. I am running 3/4 auto & 1/4 LL. That gives me the lead content of old 80 octane, and seems to ameliorate exhaust seat problems. I would never admit to using a dollop of MMO at each fueling.

Remember, we do a compression check every single flight. A Mooney gets a compression check once a year. On average, a cylinder goes bad at the six month point.

Also remember - a cylinder can go soft with a piece of junk in a valve seat, and may fix itself the next time out. Shops often yank cylinders prematurely, and on these old engines the cylinder shop will red tag it in a heartbeat.

I have had three cylinders crack over 60 years. I am replacing one today. Even with the crack, it developed full power. We watched it for two weeks before I hooked the air to it to see what was going on.

A small Continental will run forever with care - or you can pull it apart and spend $20 grand - your choice. I have had excellent luck over 6000 hours behind these things.

except for valve guides being too tight by most shops and some out of the factory causing problems with wear and thusly low compressions...I went through 5 overhauled cylinders in 125 hours on an overhauled engine, bought 4 NEW ECI cylinders and have been no problems since they were put on. These are the ones that had the exhaust rotators. Tim
 
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