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Replace pistons at overhaul???

j-red

Well Known Member
I've got a parallel valve io-360 that i'm overhauling for my 8. It's got about 1000 hours since an overhaul that happened 30 years ago. I'm tearing it down because of pitting and a severely spalled lifter. I've sent all the internals out and have gotten everything back with tags along with a reconditioned cam and replacement tappets.
There's just one last thing to find out before it goes back together...

I see that the lycoming mandatory overhaul list does not include the pistons themselves. If they are re-used, how are they cleaned of all the carbon and lead that accumulates on them? I figured that if they were being re-used, then a place like Aircraft Specialties would clean and inspect them, but I don't see pricing for that on their website like I do for all of the other internal components they will refurbish.

I'd love to save $500 and not buy new pistons if I don't have to, but i'm reluctant to stick new rings on these things without knowing for sure that they're ok to use not to mention being cleaned.

So, the questions:
Re-use them or just toss and replace?
If re-use, how are they cleaned?
Is this something I can do myself, or should they be sent somewhere?

Thanks!
 
I don?t know of a good way to clean them chemically, if you use elbow grease be careful not to put scratches in them (stress risers), especially in the ring lands. Maybe media blasting with soda would work. I don?t think you will find anyone that normally reuses them, shops would be in deeper cost wise than new. If you do reuse them make sure you check for ring land wear.
Tim Andres
 
1000 hrs on previously OH cylinders (what are the cyl total hrs?), its not really an OH if you don't replace all 4 cyl assy's. Without new cylinders its really just an engine repair not an OH.
 
1000 hrs on previously OH cylinders (what are the cyl total hrs?), its not really an OH if you don't replace all 4 cyl assy's. Without new cylinders its really just an engine repair not an OH.

Granted things may have changed in the many years since I was active in the A&P business but if one follows the engine manufactures overhaul guidelines then the engine is considered overhauled. Not true :confused:
 
Do yourself a favor and just get new cylinder assemblies, piston and rings. You won't regret it!
 
Granted things may have changed in the many years since I was active in the A&P business but if one follows the engine manufactures overhaul guidelines then the engine is considered overhauled. Not true :confused:

An "overhaul" done in "Joe Blows" hanger is not really an "overhaul" is my point. Someone that does an engine "overhaul" that does not use parts that have been approved/inspected/checked/replaced IAW the OH manual has not done an overhaul.

If were trying to figure out how to clean the pistons, I doubt they or the cylinders have been checked to see if they meet the dimensions/limits in the manual. If you're going to OH an engine you can't just pick and choose what you want to do, you got to do it all otherwise its just a repair and not an "overhaul".
 
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I would replace them. By the time you get set up to clean them you'll have as much in the equipment as a new set of pistons.

This said I have a 5-gallon stainless heated ultrasonic tank in which I use Oil Eater mixed with water. Works great but lead deposits require scraping.
 
Are Lycoming exhaust valves prone to losing their heads in old age? Separating at the stem. Something a local engine builder told me.
 
An "overhaul" done in "Joe Blows" hanger is not really an "overhaul" is my point. Someone that does an engine "overhaul" that does not use parts that have been approved/inspected/checked/replaced IAW the OH manual has not done an overhaul.

If were trying to figure out how to clean the pistons, I doubt they or the cylinders have been checked to see if they meet the dimensions/limits in the manual. If you're going to OH an engine you can't just pick and choose what you want to do, you got to do it all otherwise its just a repair and not an "overhaul".

That's just the reason for the question: I'm going "by the book", replacing the cylinders with 1st run yellow tagged standard bore cylinders, but "the book" doesn't say anything about the pistons. Rings, pins, connecting rods, everything else, yes, but not the pistons. Seems like an odd omission. I had the same question when rebuilding my last engine but instead of asking, I just replaced them. I don't mind doing that this time, but do want to get to the bottom of it.
 
An "overhaul" done in "Joe Blows" hanger is not really an "overhaul" is my point. Someone that does an engine "overhaul" that does not use parts that have been approved/inspected/checked/replaced IAW the OH manual has not done an overhaul.

If were trying to figure out how to clean the pistons, I doubt they or the cylinders have been checked to see if they meet the dimensions/limits in the manual. If you're going to OH an engine you can't just pick and choose what you want to do, you got to do it all otherwise its just a repair and not an "overhaul".

I respect your experience and knowledge but those are a lot of assumptions my friend.

Following the overhaul manual and reusing where approved and replacing when indicated is an overhaul. To say other is disingenuous.

Should the OP replace the cylinder assembles just because...maybe but the ones in hand, if within overhaul limits may be more proven than a brand new cylinder assembly.

That being said, I'm buying a new engine for my build. And if I ever get to the point of needing an overhaul, This Joe Blow might just do it himself ;)
 
If you are overhauling because of a severely spalled cam, your pistons are not useable and already ruined because you will find steel from the cam and tappets imbedded in the piston skirts....
Good Luck,
Mahlon
 
If you are overhauling because of a severely spalled cam, your pistons are not useable and already ruined because you will find steel from the cam and tappets imbedded in the piston skirts....
Good Luck,
Mahlon

Exactly what I was looking for. Thanks!
 
Thinking about eventual sale price, if you were to use complete new cylinder assemblies, when you come to sell the aircraft (whenever that is), the price you might get will likely be significantly more than the difference in cost between overhauled and new cylinders. I would install new cylinders every time, as said previously the cost difference is just not that great. Pete
 
Thinking about eventual sale price, if you were to use complete new cylinder assemblies, when you come to sell the aircraft (whenever that is), the price you might get will likely be significantly more than the difference in cost between overhauled and new cylinders. I would install new cylinders every time, as said previously the cost difference is just not that great. Pete

Interestingly, even though the Lycoming factory sells both rebuilt and overhauled engines they put new cylinder assemblies on both.
 
Overhaul

Look up the definition of "overhaul" by the FAA and you will be surprised!

Not what you would expect.
 
origional question

So, back to the original question.

Where would a guy find guidance if he wanted to "overhaul" a set of pistons?
 
I think the conclusion was that, while Lycoming doesn?t mandate replacing them, there is no guidance on how to inspect/overhaul them and thus they virtually always get replaced. At least that was my takeaway from the two or three relevant posts.
 
I think the conclusion was that, while Lycoming doesn?t mandate replacing them, there is no guidance on how to inspect/overhaul them and thus they virtually always get replaced. At least that was my takeaway from the two or three relevant posts.

25-years ago, I had an old IA that also taught A&Ps tell me to always replace the pistons at overhaul time. He said that the piston ring groves wear enough that there is a high risk of breaking rings.

I am with the other guys to replace the cylinder assembly. Overhaul price is 70% the cost of new last time I checked.

I ONCE paid a shop that use to advertise on VAF to overhaul 4 cylinders for me with new valves, springs, guides, pistons, and rings. After 11 hours trying to break the engine in, I still had LOW compression on one cylinder. The seat had separated from the head and was leaking out the exhaust. Shop would not stand behind their work so I ate the over $3K cost. 4 new cylinders cost me around $3,600. That was in the neighborhood of $400 more than what the overhaul cost was.
 
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