A look in my A75

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jesse

Touchdown! Greaser!
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Jesse
About a year ago I saw the post on one of these aviation forums about using a dental cam to look inside cylinders. I ordered one off eBay for about $20 and it sat on my desk for a good year before I decided to give it a shot.

Weather was nice today, so headed to the airport, I had to dremel most of the camera's housing away so that it would fit.

Pictures.....

Cylinder 1 Exhaust Valve
5xF6OGw.jpg


Cylinder 1 Intake Valve
Ve2GYen.jpg


Cylinder 1 Piston Face
ei61RSI.jpg


Cylinder 2 Exhaust Valve
gCCEK80.jpg


Cylinder 2 Intake Valve
YJwdvCL.jpg


Cylinder 2 Piston Face
j09d3Ox.jpg


Cylinder 3 Exhaust Valve
PZQGyGH.jpg


Cylinder 3 Intake Valve
xV6PRed.jpg


Cylinder 3 Piston Face
9iQ6ZlV.jpg


Cylinder 4 Exhaust Valve
bZ5FdBa.jpg


Cylinder 4 Intake Valve
kYqP9sf.jpg


Cylinder 4 Piston Face
lhtt9eY.jpg


I couldn't really figure out a way to get a look at the cylinder wall. You can however see pretty much anything you'd want to see with the valves including their motion as they move up and down.

Of course, I really have no clue what I'm looking at, anything concerning in these pics? Interesting how the exhaust valves in Cylinder 2 and 4 have those indentations in the center and the others don't. Different style valves?

Cylinder 3 is the "newest" and was overhauled about 50 hours ago. The rest have 400 ish hours on them.
 
100LL or autofuel?
 
James331 said:
100LL or autofuel?
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90% auto fuel since it was assembled. Avgas on cross countries a few times a year.

I run it hard all the time and lean aggressively in cruise.

Plugs always look great.

Like most single owner airplanes I don't fly it near enough.
 
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I have a ProVision 100 Optical scope, a Dewalt DCT411S Video Inspection Scope and a twenty two dollar Chinese dental camera. The dental camera is, by far, the best tool for looking at valves on aircraft engines because of the angle of the camera, the focal length and the illumination. I modified the housing so that half of it can be removed so it will fit through a spark plug hole and replaced afterwards so it can be used for other things like looking at your teeth or the hairs in your ear :D The dental cam's biggest drawback is having to tote your laptop around with it.

Now, as far as what you're looking at, just typical stuff. You're going to see a lot of carbon in these small engines as most of them don't have a mixture control or it has been disabled and wired full rich. As interesting as it is to watch the valves open and close you honestly are not going to discover anything surprising with any of these devices that would not have already been revealed by a simple compression test. By the time you see a burnt valve your compression readings are going to be absolutely dismal. You can in fact have an extremely low compression reading due to a leaky exhaust valve and very likely not be able to detect anything visibly wrong - even if you pull the jug and look down in there with your bare eyes and a bright light.

I know all about the manufacturer's service letters and the pictures in them that savvy maintenance uses to make the claim that a borescope inspection trumps the tried and true compression test but not in my experience. For one thing, not one of those photos was taken with a borescope or dental cam, they are all of cylinders that were removed because they had ZERO compression.

Now there are uses for these tools such as looking under floors, in wing sections and reading the serial numbers off of magneto, carb and other component dataplates that might in awkward, hard to see positions but I dispute the idea that they are "must have" tools for engine inspections.

DSCN9554.JPG
 
Silvaire said:
I have a ProVision 100 Optical scope, a Dewalt DCT411S Video Inspection Scope and a twenty two dollar Chinese dental camera. The dental camera is, by far, the best tool for looking at valves on aircraft engines because of the angle of the camera, the focal length and the illumination. I modified the housing so that half of it can be removed so it will fit through a spark plug hole and replaced afterwards so it can be used for other things like looking at your teeth or the hairs in your ear :D The dental cam's biggest drawback is having to tote your laptop around with it.

Now, as far as what you're looking at, just typical stuff. You're going to see a lot of carbon in these small engines as most of them don't have a mixture control or it has been disabled and wired full rich. As interesting as it is to watch the valves open and close you honestly are not going to discover anything surprising with any of these devices that would not have already been revealed by a simple compression test. By the time you see a burnt valve your compression readings are going to be absolutely dismal. You can in fact have an extremely low compression reading due to a leaky exhaust valve and very likely not be able to detect anything visibly wrong - even if you pull the jug and look down in there with your bare eyes and a bright light.

I know all about the manufacturer's service letters and the pictures in them that savvy maintenance uses to make the claim that a borescope inspection trumps the tried and true compression test but not in my experience. For one thing, not one of those photos was taken with a borescope or dental cam, they are all of cylinders that were removed because they had ZERO compression.

Now there are uses for these tools such as looking under floors, in wing sections and reading the serial numbers off of magneto, carb and other component dataplates that might in awkward, hard to see positions but I dispute the idea that they are "must have" tools for engine inspections.

DSCN9554.JPG
Click to expand...

I basically just cut the housing off mine past the button for the light and then covered it in electrical tape:
jrk5ZwVl.jpg
 
I ordered a dental camera over a month ago and hoped to get a good look at my engine at annual. But the engine is done and buttoned back up and no dental camera yet.

It's likely sitting in the big parking lot of ships off the coast of Long Beach.
 
Pretty neat, Jesse.

Makes me want to get one and use it on my jet ski, just because.
 
From the little I know about this, that first photo looks a little suspicious.

I think it may show uneven heating, which may show the valve is not quite seating properly.

I think.
 
Cylinder 1 and 2 exhaust valves need to be lapped, they are starting to leak, but right now you can likely fix it in place with a drill motor and lapping compound, I would do the exhaust on 3&4 as well, I don't have a good enough view to say you have a good seal on those.
 
Henning said:
Cylinder 1 and 2 exhaust valves need to be lapped, they are starting to leak, but right now you can likely fix it in place with a drill motor and lapping compound, I would do the exhaust on 3&4 as well, I don't have a good enough view to say you have a good seal on those.
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Not doubting you, but for my own education, what in the pics brings you to that conclusion?
 
jesse said:
Not doubting you, but for my own education, what in the pics brings you to that conclusion?
Click to expand...

The uneven darkening at the edge. It means those spots aren't getting as hot as the spot next to it. This is caused by carbon deposits insulating there. Eventually what will happen is that carbon will get thick enough to chip a gap, and then a jet of combustion gas will shoot through it and erode the valve away. This is how "burned valves" happen. You'll never see an intake valve problem unless you ingest something or something breaks.
 
jesse said:
Not doubting you, but for my own education, what in the pics brings you to that conclusion?
Click to expand...

nothing, doesn't scares me. looks normal.
 
None of the valves look burnt, and if it's holding compression and running good, run it.

"if it ain't broke, don't fix it."

:yesnod:
 
Henning said:
The uneven darkening at the edge. It means those spots aren't getting as hot as the spot next to it. This is caused by carbon deposits insulating there. Eventually what will happen is that carbon will get thick enough to chip a gap, and then a jet of combustion gas will shoot through it and erode the valve away. This is how "burned valves" happen. You'll never see an intake valve problem unless you ingest something or something breaks.
Click to expand...

Sorry Henning, I've got one of these cameras and there is no way you can see anything as detailed and meaningful as you describe. What you think you are seeing completely changes by turning the camera head a few degrees. Anyone who'd let you monkey with their valves based on these pictures would be a complete idiot. As I said earlier, if you see discoloration (with a real borescope or by actually looking down the barrel of a removed cylinder you'd already have witnessed dismal results from a standard differential compression test.

They're fun, they're twenty bucks but a serious or particularly useful diagnostic tool they are not.
 
timwinters said:
I ordered a dental camera over a month ago and hoped to get a good look at my engine at annual. But the engine is done and buttoned back up and no dental camera yet.

It's likely sitting in the big parking lot of ships off the coast of Long Beach.
Click to expand...

China Post, normally takes 45-60 days. It was free wasn't it? Probably ships to Vancouver or Mexico then comes on a truck, pretty much what nafta was all about so never sees Long Beach.

I think it took 60 days for mine to arrive.
 
Silvaire said:
China Post, normally takes 45-60 days. It was free wasn't it? Probably ships to Vancouver or Mexico then comes on a truck, pretty much what nafta was all about so never sees Long Beach.

I think it took 60 days for mine to arrive.
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Actually, I got two cell phone batteries direct from China in two weeks or less each (separate orders about a month apart).

I was amazed.
 
timwinters said:
Actually, I got two cell phone batteries direct from China in two weeks or less each (separate orders about a month apart).

I was amazed.
Click to expand...

When you ordered, the batteries were already on shore.
 
Silvaire said:
Sorry Henning, I've got one of these cameras and there is no way you can see anything as detailed and meaningful as you describe. What you think you are seeing completely changes by turning the camera head a few degrees. Anyone who'd let you monkey with their valves based on these pictures would be a complete idiot. As I said earlier, if you see discoloration (with a real borescope or by actually looking down the barrel of a removed cylinder you'd already have witnessed dismal results from a standard differential compression test.

They're fun, they're twenty bucks but a serious or particularly useful diagnostic tool they are not.
Click to expand...

Nailed it, both counts !
 
Silvaire said:
Sorry Henning, I've got one of these cameras and there is no way you can see anything as detailed and meaningful as you describe. What you think you are seeing completely changes by turning the camera head a few degrees. Anyone who'd let you monkey with their valves based on these pictures would be a complete idiot. As I said earlier, if you see discoloration (with a real borescope or by actually looking down the barrel of a removed cylinder you'd already have witnessed dismal results from a standard differential compression test.

They're fun, they're twenty bucks but a serious or particularly useful diagnostic tool they are not.
Click to expand...

He could just smear some Devcon on it and call it good.....:wink2:
 
Tom-D said:
When you ordered, the batteries were already on shore.
Click to expand...

Ummm no...like I said, they came from China (Hong Kong to be exact)...tracked them the whole way...
 
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