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Cylinder walls, reflection or corrosion?

N427EF

Well Known Member
I am doing a little housekeeping, oil change, filter change oil screen inspection and while I am waiting to receive my Monkworkz generator, I decided to bore scope my cylinders and valves. I usually do this for my annual but it can't hurt to get it done a bit early.
What I am looking at is the white speckles at the bottom of the cylinder walls.
Is this a reflection of some sort or some kind of carbon debris, corrosion maybe ? The valves look normal the way they always do and the cylinders appear to be normal as well with their typical burn patterns. The cylinder walls also show a nice looking cross hatch but I can't remember seeing these white speckles before? It appears that the front cylinders 1 and 2 have more of these speckles than those further back, 3, 5 , 4 and 6.
Oil consumption is normal, filter and screen is clean and all runs normal at 709 hours of operation. Just wondering what those white spots could be???
For those interested, the scope is a Teslong Digital Endoscope Model MS450-NTC
What say you?
 

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Spots

I believe the spots are just the reflection off the top edges of the pistons.
Jim Baker
N699JB
RV-6
 
Thanks

Thanks Jim,
Cameras and light sources can play tricks I guess.
I often look at the carbon deposits that break off in different places and sometimes it appear as though a piece of the piston broke off.
 
No its rust. Very common to see even if the airplane sits a few weeks. Fly it and forget about it.
 
No its rust. Very common to see even if the airplane sits a few weeks. Fly it and forget about it.

+1

When you get corrosion spots like that, a thou more or less of metal turns to rust and later disappears, leaving a crater. Once this happens, the ring no longer rides on that surface and it will appear dull compared to the shinny stuff where the ring is polishing the wall surface. Same concept as the cross hatch line, which is dull and why you are able to see it.

Pic 2 is showing corrosion spots and pic 3 is showing a reflection of the piston crown (can see a perfect mirror image of piston top) and also a good example of glazing above that reflection.

Larry
 
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Glazing?

Thanks for the input, it was too good to be just a reflection I guess.
I wasn't concerned and flying more is probably the only way to prevent more of that spotty corrosion.
Larry, what makes you see glazing?
The brownish look of the cylinder wall?
Glazing or not, this engine has had a very steady 10 hours/qt of oil since new.
I am not aware of what others are seeing but it seems fairly normal oil usage for a 6 cylinder engine?
It has been 12 years since first start up and 710 hrs since new.
 
Thanks for the input, it was too good to be just a reflection I guess.
I wasn't concerned and flying more is probably the only way to prevent more of that spotty corrosion.
Larry, what makes you see glazing?
The brownish look of the cylinder wall?
Glazing or not, this engine has had a very steady 10 hours/qt of oil since new.
I am not aware of what others are seeing but it seems fairly normal oil usage for a 6 cylinder engine?
It has been 12 years since first start up and 710 hrs since new.

The transluscent tan/brown stuff in pic 3 is glazing. There is a only a small amount of it, so no surprise that oil consumption is in the normal category. However, some see 20 hrs/qt and this type of limited glazing is probably part of the reason why you only get 10. It formed in the first hour or two of running, so would not expect it to change oil consumption over time. This is a pretty small patch and all the way at th bottom of travel, so not surprised that you see no other symptoms, like oilly plugs. Nothing really to be concerned about, beyond the higher oil consumption. No long term negative effects. I only pointed it out as a learning opportunity for readers.

I will say that glazing can cause excessive carbon deposits in the ring land. So, if you ever experience a spike in oil consumption, follow Mike bush's flush procedure to unstick the rings. It will most likely be the cyl with glazing.

Glazing is often seen in pathces like this and often limited to one or two cylinders.

Larry
 
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