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cylinder wall rust

vluvelin

Well Known Member
Today during pre-purchase decided to look in to cylinders of perfectly flying RV
and was sure it is perfect!!! IO360 had adequate power well balanced cylinders
(no abnormal vibration). But was disappointed. To my understanding it is
petted too deeply, honing is not visible. Compression was checked using automotive compression tester 150psi +/- 5


Need opinion of knowledgeable people. How much corrosion is acceptable???
cyl_1
Cel1.jpg

Cyl_2
cel2.jpg

Cyl 3
cel3.jpg
 
The answer is none. No tolerance for corrosion.

But, Ok so lets talk realistic, not new motor desires/specs. You have to evaluate youre tolerance for risk.

What youve got is not optimal, but not in and of itself is a killer if compressions are good. That is to say the motor wont self destruct just because of this specifically, not now and not ever really. It may eventually start eating up oil if its not doing it already, or pollute the oil quicker than it should. To be explicit, a motor can run fine with zero static compression, will even run ok w/o piston rings. But it'll drink oil, make lots of blow-by and obviously wont make the kind of torque/power it should. Clearly noone would want that extreme for an airplane - obviously.

But what the cylinder rust in all cyls does is make the entire motor suspect to other items that must be looked at. Most importantly, is to get a look at is the cam for a def go/no go. Any pitting on the cam and its a rebuilder for sure. Then to: Does the motor have oil analysis history? Then to a current oil change, oil analysis of that sample, and cutting the filter.

If it has a CS prop, I'd pull that for sure and look at the sludge for a warm fuzzy. Thats a clear historical story on the motor, like a core sample. If you got rust particles in that, its been all through the motor, and is imbedded in the crank bearings, its a rebuilder IMHO.

If everything checks out ok except for the cylinder walls, I'd prob buy it, negotiate for a lower price and change out the cylinders anyway.....or if I felt ok about it, at some point when compressions, blow by or oil use indicates it. Prob wouldnt open up the bottom tho.

Of course, caveats right? Not telling you what to do, and this just my .02; just food for thought.
 
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I have honed my own cylinders that had light rust and become polished and lost the hone pattern but they were not nearly as bad as what you've shown.
http://forum.canardaviation.com/showpost.php?p=69231&postcount=40

I bet he's using oil. Lycoming says 2 qts/hour is the max; higher than that can promote detonation. Better factor a cylinder overhaul into the price.

Its different for different engines, and different depending on what %HP youre running. Pretty sure at 2qt/hr you'll be oil fouling plugs and messing your belly pretty bad.......
 
Where has it been stored? It is not a safety issue. I would be much more concerned about the cam. That rust is from sitting idle and the cam is the most susceptible. If you can get it at a fair price there is no safety concern what-so-ever to fly it and keep an eye on your oil analysis to see if you have a problem. Just get it at a price that you won't be upset if you have to do an overhaul sooner than later.
 
Thank you for responce what is
warm fuzzy??

Lol. Sorry. It means a "good feeling".....cant remember where I picked that one up from....I think it originates from the feeling you get from hugging a warm fuzzy...... blanket, pillow, small animal etc....
 
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Lol. Sorry. It means a "good feeling".....cant remember where I picked that one up from....I think it originates from the feeling you get from hugging a warm fuzzy...... blanket, pillow, small animal etc....

in this context i understand
was thinking some thing about CSprop that i didnt know
 
there are spots of rust that are glazed over looks like they were there for longer time then others.
rust looks fresh in most cases.

engine is around 300 hours sins New
Rings still holding no signs of excessive blow-by as i understand that dont take long to graind rings 100 hours???
 
in this context i understand
was thinking some thing about CSprop that i didnt know

If you found something warm and fuzzy in the tunnel to the CS prop, then that would be a motor built with mouse power. Youd want to talk to Walt Disney in that case! :)
 
there are spots of rust that are glazed over looks like they were there for longer time then others.
rust looks fresh in most cases.

engine is around 300 hours sins New
Rings still holding no signs of excessive blow-by as i understand that dont take long to graind rings 100 hours???

Graind rings? Ok your turn. Whats that mean? Its usually ionly 10hrs orless for rings to seat these days. Noone builds with Chrome rings much anymore, so I'd doubt you have those.

If the motor only has 300hrs and has been flown regularly each month since inception (say 5-6hrs/mo), I'd bet my I-teeth that the builder put those crappy cylinders on right outta the box and hid it from the buyer..... and if that is the case theres some good history of it not being much of an issue for this particular motor. Again oil analysis since inception would be key for me then.
 
Iwas talking about rust and rings interaction will manifest itself in to blow by
and oil burning

there is no info on how much it was flown or how often.
it was assembled from Superior Kit by Penn Yan. that is the only info i can get

sorry for my English
 
Originally Posted by maniago View Post
If it has a CS prop, I'd pull that for sure and look at the sludge for a warm fuzzy.


I used to pull 2 Hartzell props every 3 years for a recurrent AD. Never ever pulled one that did not have lead paste inside the front of the crank. It is normal to see that gray sludge in there.
 
Originally Posted by maniago View Post
If it has a CS prop, I'd pull that for sure and look at the sludge for a warm fuzzy.


I used to pull 2 Hartzell props every 3 years for a recurrent AD. Never ever pulled one that did not have lead paste inside the front of the crank. It is normal to see that gray sludge in there.

Yes, this is normal maintenance to remove sludge from the crank. It's in the Hartzell manual.

By the way, a "motor" is not internal or external combustion. That is called an engine!:D
Motor... a machine that converts electrical energy into mechanical energy by means of the forces exerted on a current-carrying coil placed in a magnetic field.:rolleyes:
 
Looks like some good information.

Not leading to catostropic failure
Oil consumption will be first indicator
serious enough to consider other damage internally
look at oil samples to be sure.

Conclusion: make offer on plane if you love it, but discount by 75% of what an overhaul would cost assuming new jugs and pistons. then fly and do oil samples and compression (leak down) checks to monitor health. In cylinder inspections are a must on a regular basis.
 
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