4 Pistons 2 different part numbers.

SixPapaCharlie

SixPapaCharlie

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Lycoming 0320 with STC high compression pistons (160 HP)
In recent months, 2 pistons were replaced but the part number is slightly different.

2 Pistons are part number SL75089 and 2 Pistons are part number SL75089P10
My concern (and I will call the MX tomorrow) is finding out if these are the same but maybe the part number changed over time.

I'd hate to find out that the engine was STC for high compression pistons but when 2 of them were replaced in an overhaul they replaced them with the standard non high compression pistons.

Anyone know what that P10 indicator is on two of the pistons?

Hopefully they were savvy enough to discern that this engine is 150 HP by default and not 160 and knew to replace pistons with the STC'd High compression pistons and not grab standard pistons for replacement.

Thanks
 
I don't believe you need to be concerned.
The P10 means the pistons are oversized by 10 thousandths of an inch. This is standard part nomenclature for Lycoming - a "P" means oversized, an "M" means undersized part
Presumably the cylinders were reconditioned and the bore is thus oversized, hence the need for the oversized pistons.
Other than this small difference in diameter the pistons are all identical.
 
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Thank you so much @GRG55

This is a lot to take in and try to decipher.
Anything here that you would consider a red flag?

Engine Doc.jpg
 
6PC ,I am somewhat perplexed by your post.you have been here for a long time and posted 11k times .your answer was in the work order why the fuss? btw great way to get a "overhall" your insurance pays 8k and you pay3k for parts.anybody in the know would accept that as a 0 tsoh .
 
6pc ,who's stc are you using ? does it have a limit on full power stated in a placard, as time ? what airframe?
 
@hotprops, I am not sure I understand...
AA5A airframe.

I am looking at a plane and gave this doc to a local. He raised the question about the 2 different part #s for the pistons.
I am not sure if there is an issue. He stated to me I should verify that the 2 diffrent part numbers did not mean 2 high compression pistons and 2 standard pistons.

I fly out Saturday to look at the logs at which point, I will be able to compare the logs
 
it says in the wo 10 over on the 2 cylinders .reading is fundamental
 
There are others here who are far more knowledgable in the specifics of overhauling aircraft engines than I am. Here's what I can tell you:

The engine suffered a prop strike, which in Lycomingspeak is a "sudden stoppage". Lycoming has a very detailed inspection procedure that is supposed to be followed in that event, Service Bulletin 533C. Here's a link if you need some reading to help you get to sleep one night:

https://www.lycoming.com/sites/default/files/SB533C Recommended Action for sudden Engine Stoppage, Propeller_Rotor Strike or Loss of Propeller_Rotor Blade or Ti (1).pdf

Sounds like the engine was in pretty rough shape, probably from sitting too long. A lot of internal corrosion as evidenced by the rejection of the crankshaft (the referenced AD is corrosion related) and the spalled camshaft. That's an indication the airplane sat for some time, developed corrosion pits on the camshaft hardened surface and then was flown enough to break down and spall the cam.

Looks like one cylinder was replaced as it was cracked near a spark plug hole - not that unusual. List of work and parts looks as one would expect for a prop strike and the internal corrosion problems found. Please note this is not an overhauled engine but an IRAN, at least the way I read the work order. That means the engine time since major overhaul continues instead of being re-set to zero. However, if the new rings and bearings are broken in properly, and the engine is flown and maintained properly it should get to TBO or beyond.

Hope that helps.
 
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SixPapaCharlie said:
@hotprops, I am not sure I understand...
AA5A airframe.

I am looking at a plane and gave this doc to a local. He raised the question about the 2 different part #s for the pistons.
I am not sure if there is an issue. He stated to me I should verify that the 2 diffrent part numbers did not mean 2 high compression pistons and 2 standard pistons.

I fly out Saturday to look at the logs at which point, I will be able to compare the logs
Click to expand...

The pistons are not an issue at all. They are identical in every respect except for the 10 thousandths of an inch oversize diameter.

The repair did not replace all the cylinders with new cylinders. Three of the existing cylinders were re-used and the fourth was a reconditioned cylinder. It is normal in this situation to hone the cylinders (so the new rings will seat properly on break in). Two of the cylinders were bored .010 inch over. That's usually done if there is some light scoring or similar that must be removed from the cylinder wall. Again not unusual when a cylinder has been in service. The oversized pistons are needed to deal with the bored cylinder dimension increase.

What you have here is the next best thing to a freshly overhauled engine.
 
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Yes. I'm flying up Sat. and returning Sun.
3rd time flying across country to look at a plane. Hopefully 3rd time is the charm.
 
Good luck, hope it works out for you! Fly the cirrus up and show them you mean business.
 
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Regrind the cam and followers after spalling was discovered? That's not what I'd want. Just sayin'.
 
Stewartb said:
Regrind the cam and followers after spalling was discovered? That's not what I'd want. Just sayin'.
Click to expand...

You would probably replace the cylinders and pistons with new also?

It's an IRAN, not an overhaul.
 
I mistakenly used the term overhaul in my original post. I don't always choose my words as though they're going to be scrutinized by attorneys LOL yes consider this a repair.
 
SixPapaCharlie said:
I mistakenly used the term overhaul in my original post. I don't always choose my words as though they're going to be scrutinized by attorneys LOL yes consider this a repair.
Click to expand...

I feel a "How to Overhaul Your Airplane Engine Over Your Lunch Hour" satire video coming...
 
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