Borescope horoscope

[LifeAsBen]

Complete noob here! I purchased a 1950 C140A (w/ C-90 engine) and got right to work borescoping my exhaust valves. All compressions are in the 70's.

I'm certain this topic will generate a lot of discussion and debate, so please...go ahead tell me my engine is about to eat a valve or that I'm crazy and should just fly it. I need experienced, educated opinions!

Cylinder 1:

Cylinder 2:

Cylinder 3:

Cylinder 3 closer look:

Cylinder 4 (new cylinder, 15hrs):

 

[Bell206]

. I need experienced, educated opinions!

A good starting place. Download the chart.
https://www.aopa.org/training-and-safety/air-safety-institute/valve-safety

 

[Craig]

2 and 3 would concern me enough to get a better scope on them before making a judgement. If a better scope can’t be had in a reasonable amount of time, I would pull them and tear them down for a better look.

Most of the lower cost scopes just don’t have as good optics as the better ones. 99% of the time, the better ones are not needed. There are times at work, even using a 90k$ scope doesn’t work out as well as being able to put a direct eyeball on things.

 

[Timbeck2]

#3 looks like just some carbon build up that has sloughed off leaving the shiny looking areas. You have a normal looking bullseye pattern on all of them. But as Craig said above, I'd get a second opinion with a better scope. I think you may be worrying about nothing.

 

[steingar]

I think I might have boroscoped them before purchasing the airplane, but that's just me.

 

[Robert Gee]

Congrats on your plane.
Its likely a case of "what you dont know won't hurt you" Its carbon build up from running rich and loping along, it layers upon itself then breaks off in chunks sometimes blocking a valve from closing or scoring the cylinder walls and most times completely harmless. If it were mine or a car engine Id spritz water, trans fluid or the best toxic snake oil available, KREEN, into the carb. Smoke the mosquitos and clean that out.
I think a better check-on thing would be an oil analysis.

Id like a real MX to comment if this is another good reason to run MoGas is these older, low compression engines.

 

[Silvaire]

First off, that's not a borescope. Secondly, who in their right mind is going to start pulling cylinders with perfectly good compression readings based on a fuzzy picture from a cheap Chinese dental camera?

 

[RyanB]

I don’t see it mentioned, so I’ll ask - what brings up the desire to borescope? Just for the sake of being curious, or is the engine not running right?

If all of your compressions are in the 70’s, I really wouldn’t lose any sleep over it and I certainly wouldn’t go to the trouble (and expense) of pulling cylinders (assuming everything is running fine).

 

[Huckster79]

Go get some Mogas, clear prop and clean her out!

Welcome aboard! I’m a 140 guy too but not all fancy w an A model

I recall my first few months of ownership I was scared to death something was wrong with her at every corner, primarily from the horror stories some folks like to tell ya. Owning one I found a d being good at it is as much a learning curve as learning to fly them.

 

[LifeAsBen]

First off, that's not a borescope. Secondly, who in their right mind is going to start pulling cylinders with perfectly good compression readings based on a fuzzy picture from a cheap Chinese dental camera?

Hahaha point taken…. I’m getting a better scope

 

[LifeAsBen]

I don’t see it mentioned, so I’ll ask - what brings up the desire to borescope? Just for the sake of being curious, or is the engine not running right?

If all of your compressions are in the 70’s, I really wouldn’t lose any sleep over it and I certainly wouldn’t go to the trouble (and expense) of pulling cylinders (assuming everything is running fine).

It’s running fine. Because borescope is only way to really know the health / condition of valves.

 

[LifeAsBen]

Go get some Mogas, clear prop and clean her out!

Welcome aboard! I’m a 140 guy too but not all fancy w an A model

I recall my first few months of ownership I was scared to death something was wrong with her at every corner, primarily from the horror stories some folks like to tell ya. Owning one I found a d being good at it is as much a learning curve as learning to fly them.

My plan is to run mogas! But educating myself first…and what I’ve discovered is I need to determine if valve seats are hardened by it was rebuilt early 2000’s. I assume they are but I want to be certain.

 

[LifeAsBen]

A good starting place. Download the chart.
https://www.aopa.org/training-and-safety/air-safety-institute/valve-safety

Oh awesome I haven’t seen this, thanks!!

 

[Huckster79]

My plan is to run mogas! But educating myself first…and what I’ve discovered is I need to determine if valve seats are hardened by it was rebuilt early 2000’s. I assume they are but I want to be certain.

Someone more qualified than I could speak to this probably better, but I’ve read repeatedly that lead is there to raise the octane- period, not for lube not for valve seats…. I could be wrong but it makes sense to me. If your engine qualifies for the STC for mogas… clear prop on mogas.

your engine and mine was definitely not designed to burn 100LL… that I can say for sure- interesting we all don’t need an STC to run 100LL in engines not designed for it- but that’s another days soapbox. 100LL has an obscenely high lead content to boost the octane, something like four fold the lead the 80/87 octane our little continentals were designed for had in it.

There’s some good info on our little continental engines on the a site for flybabies.

btw on mogas I found a great way to test for ethanol- was put some gas in a pop bottle and a few drops of water based food color, shake the devil out of it as bob ross would say… if you have gas colored like the food color take that rec fuel home and don’t dump it in the plane- the food color blended with ethanol. If you still have beads of food color- clear prop. I’m guilty too much of using 100 LL for convenience but I swear my c85 runs smoother on mogas, I get mine from a Walmart station in town, never found any ethanol in any load I’ve got. Also some folks like to add some 100ll to the tanks as well at a 1:3-1:4 ratio to mogas- that kinda gives the ol continental gas that has the amount of lead she was built for.

do know mogas does not have the shelf life 100LL has so fly frequently or if you won’t be- fill her with 100LL.

 

[Albany Tom]

That's a great test for ethanol, hadn't heard of it before, thanks! Much easier than measuring and adding water.

 

[Silvaire]

It’s running fine. Because borescope is only way to really know the health / condition of valves.

That's actually not true. If you look inside with a camera of some sort and see what is obviously a burnt valve I can guarantee you that the compression reading on that cylinder is going to be zero or darn close to it. I've pulled a cylinder off that had 20/80 compression and even with eyes down the open end of the cylinder and a bright flashlight there was no visible indication that there was a thing wrong with it. The differential compression leak-down test is very much like the canary in the coal mine analogy. It's going to be your first reliable indication of something going south.

 

[Huckster79]

I use mine at spark plug rotation just to check in general valve health looking for green or other signs… it’s just another tool in the toolbox.

my crosshatching is about shot but compressions are still good so I just look past that for now.

 

[Clip4]

Complete noob here! I purchased a 1950 C140A (w/ C-90 engine) and got right to work borescoping my exhaust valves. All compressions are in the 70's.

I'm certain this topic will generate a lot of discussion and debate, so please...go ahead tell me my engine is about to eat a valve or that I'm crazy and should just fly it. I need experienced, educated opinions!

Cylinder 1:

Cylinder 2:

Cylinder 3:

Cylinder 3 closer look:

Cylinder 4 (new cylinder, 15hrs):

Looks like a molecular cohesion problem from a sub atomic imbalance.

 

[LifeAsBen]

That's actually not true. If you look inside with a camera of some sort and see what is obviously a burnt valve I can guarantee you that the compression reading on that cylinder is going to be zero or darn close to it. I've pulled a cylinder off that had 20/80 compression and even with eyes down the open end of the cylinder and a bright flashlight there was no visible indication that there was a thing wrong with it. The differential compression leak-down test is very much like the canary in the coal mine analogy. It's going to be your first reliable indication of something going south.

Thanks the perspective!

 

[Doug Reid]

Some of the inexpensive cameras have really good resolution.

It helps to know what to look for

 

[GeorgeC]

I purchased a 1950 C140A