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Old 05-06-2014, 05:15 AM
designerX designerX is offline
Join Date: Sep 2005
Posts: 149
Default Cylinder #3 scoring, normal wear or something else? Dental cam pics.

Running a compression check on an XIO-320 D1A (200 hours since rebuild) with .010 overbore steel cylinders shows that #3 compression is down to 68/80 cold and 70/80 hot (last year it read 74/80 cold.)

During compression check air can be heard in the case by opening the oil filler, I assume is blowing by the rings on #3.

Armed with a newly acquired eBay dental camera marks can be seen at the 12 o'clock portion of this cylinder (within the nice hone/hatch marks.)

The spark plug was generally clean but did have a couple very small kernels of lead. The wear appears to be barely deeper than the cylinder cross hatching but is hard (impossible) to discern w/the magnified images.

Here is an image of the 6 o'clock position of cylinder #3.

Stan Smith
RV-8 slow build fuselage w/showplanes fastback
RV-4 (bought flying)

Last edited by designerX : 05-06-2014 at 05:48 AM.
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Old 05-06-2014, 07:06 AM
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rocketbob rocketbob is offline
Join Date: Jun 2006
Location: 8I3
Posts: 3,768

Something's not right there, I would pull that cylinder and have a looksee. In the first pic that much wear at 200 hours is not right.

Please don't PM me! Email only!

Bob Japundza CFI A&PIA
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Old 05-06-2014, 09:02 AM
lr172 lr172 is offline
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 6,728

I agree with Bob, that cylinder needs to come off. My speculation is that something is stuck in a ring gap or something like that. It almost looks like you have a concentration of deep vertical scratches caused by something going up and down with the ring and causing the gouge. The second pic shows a typical example. In the first picture, it looks like the offending defect is rotating slightly, making me think it is the ring itself or something lodged or stuck to the ring. Either way, that cylinder is likely going to need a re-bore.

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Old 05-06-2014, 09:12 AM
deek deek is offline
Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
Posts: 378

I don't know about the cylinder, but your camera images are excellent! Care to share the e-bay link?
'83 LongEZ - N888EZ 3,371 hours (sold)
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Old 05-06-2014, 09:39 AM
larryvj larryvj is offline
Join Date: Nov 2009
Location: Ocala, FL
Posts: 8

The dental camera has lots of magnification. Look at size of crosshatch. Also, LED lights may give reflections that make it look worse.
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Old 05-06-2014, 10:44 AM
Join Date: Mar 2008
Location: Seattle
Posts: 1,412

That's some good photography.
Sometimes the pic makes things look worse than they are.
Did you try to feel the scratches in the bottom with something like a dental pick? you can feel very small scratches.
On the other hand, you have measurable loss of compression. It's still in the 'safe to fly' reading, but I agree with Bob and Larry. If you are tool handy you can save your self a lot of time, money and worry.
Scott Emery
EAA 668340, chapter 326 & IAC chapter 67
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Old 05-06-2014, 11:17 AM
Tom Martin Tom Martin is offline
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,591

I had some of the ECI cylinders that were part of the recall. When we took them off we found a similar pattern to what you are seeing and it was caused by the coating on the rings that had delaminated. Apparently this was also and issue that ECI had for a short time period. I has since been corrected. I wonder if this could be your issue?
Tom Martin RV1 pilot 4.6hours!
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EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
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Old 05-06-2014, 12:55 PM
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DanBaier DanBaier is offline
Join Date: Mar 2009
Location: Rochester NY
Posts: 703

The dental cams can make minor (read normal) things look awful in a cylinder.

With that said, your photo #1 is showing something that looks unusual. If I had that wear pattern (ie., discernible and unique to only that cylinder) and leakage past the rings, I'd pull the cylinder and take a look.

RV7A (N7101) - Flying 10/2008
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Old 05-06-2014, 01:47 PM
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Titan-Xpert Titan-Xpert is offline
Join Date: Mar 2014
Location: San Antonio Tx
Posts: 51


I have seen this wear pattern many times over the years, it?s can be caused by rapid expansion of the piston caused by leaning too quickly, rapid cooling of the cylinder by reducing power quickly or a cooling system that is not functioning well. The scratches are in the thrust plane only. I would suggest to you that this cylinder is not going to heal itself it is only going to get worse; it should be removed and repaired.
Once it is removed you will probably find the thrust face of the piston scratched and the rings as well. If you measure the piston to cylinder wall clearance and ring to ring land clearances and they are with in tolerances the piston can probably be reused. If it is not in spec it should be replaced.
If the scratches can be removed by light honing (Not de glazing), replacing the rings and running-in the cylinder will bring back the lost compression.
Bobby Looper
Titan Expert-Customer Support
Email Titan Support
Continental Motors Inc.
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Old 05-06-2014, 09:27 PM
designerX designerX is offline
Join Date: Sep 2005
Posts: 149
Default Thanks for the helpful replies

Thank you all for your replies! I plan to remove this cylinder and go from there.

Tom, I checked for ECi parts.. the cylinders are Lycoming and the pistons are Superior.

Excellent Bobby, I was hoping someone out there had seen this same wear pattern. I have cut the throttle at altitude and tried gliding... I had read through the years that our tightly cowled RVs were generally immune to the shock cool? When you say leaning too quickly.. do you mean too aggressively (over leaning?)

For those inquiring about the dental camera here is a link to a newer version of the one purchased (and by the same seller) . Note: the head of the camera housing must be cut which is easy and documented somewhere in the Forum.
Stan Smith
RV-8 slow build fuselage w/showplanes fastback
RV-4 (bought flying)

Last edited by designerX : 05-07-2014 at 11:36 AM.
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