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  #1  
Old 09-28-2017, 04:54 PM
vluvelin vluvelin is offline
 
Join Date: Dec 2013
Location: Montreal
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Angry cylinder wall rust

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

Cyl_2

Cyl 3
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  #2  
Old 09-29-2017, 07:26 AM
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maniago maniago is offline
 
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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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Last edited by maniago : 09-29-2017 at 08:54 AM.
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  #3  
Old 09-29-2017, 07:47 AM
Kent Ashton Kent Ashton is offline
 
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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/show...1&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.
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  #4  
Old 09-29-2017, 08:53 AM
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maniago maniago is offline
 
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Quote:
Originally Posted by Kent Ashton View Post
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/show...1&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.......
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  #5  
Old 09-29-2017, 09:03 AM
vluvelin vluvelin is offline
 
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Quote:
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.
Thank you for responce what is
warm fuzzy??
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  #6  
Old 09-29-2017, 09:06 AM
pa38112 pa38112 is offline
 
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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.
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  #7  
Old 09-29-2017, 09:07 AM
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maniago maniago is offline
 
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Quote:
Originally Posted by vluvelin View Post
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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Last edited by maniago : 09-29-2017 at 09:14 AM.
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  #8  
Old 09-29-2017, 09:16 AM
vluvelin vluvelin is offline
 
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Quote:
Originally Posted by maniago View Post
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
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  #9  
Old 09-29-2017, 09:18 AM
vluvelin vluvelin is offline
 
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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???
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  #10  
Old 09-29-2017, 09:30 AM
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maniago maniago is offline
 
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Quote:
Originally Posted by vluvelin View Post
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!
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