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Valveoscopy

339A

339A

Well Known Member
This post is an update to the earlier one I called Tool Deathmatch in which I discovered the "cheap" Chinese dental camera.

Well with 339A down for some maintenance (the nose wheel is getting the Anti Splat Bearing Mod, should have it back before LOE. Thanks Allan.) and with some spare time on my hands, I finally managed to perform a Valveoscopy on the H2AD. This engine has a total time of 1810 hours on it, of which 1125 belong to 339A. A compression check before starting the Valveoscopy showed the following: #1 78/80, #2 78/80, #3 78/80, & #4 75/80. #3 exhaust valve, which had been my problem child, still remains good!

With my Chinese Valvescope in hand, I began the surgical procedure and managed to snap the following pictures. What I'm interested in is educated comments/opinions on the internal condition of my engine. I know there are several knowledgeable Engine Gurus on here (you know who you are), and maybe we might all learn something. My internal engine experience is zero, but I didn't notice any cracks or serious discoloration in the valves that concerned me. Although #4 exhaust face looks like it has the measles, and there seems to be a lot of lead buildup on everything? Hopefully this might motivate others with high engine times to take a look and dig a little deeper.

I have created a Picasa Web album instead of trying to post all the pics on here. Here are a few of what I consider to be the more interesting ones.

#1 Exhaust Valve Face

1exhaust.jpg


#1 Exhaust Seat

1exseat.jpg


#1 Top Plug Hole

1topplug.jpg


#3 Exhaust Seat

3exseat3.jpg


#3 Intake Stem

3instem.jpg


#4 Exhaust Face looks like it has the Measles.

4exface.jpg


Thanks for looking, and hopefully some good will come out of this thread. :cool:

Regards,
 
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Rust?

I wonder if that is corrosion on the valve that appears as red specs?
Also can you tell us how you run the engine,ie LOP or ROP?
Thanks for the info, gotta get me one of those!
Tim
 
I don't know a lot about engines, but those are great pics and I see no cavities. May need to add a Chinese dental camera to my tool box.
 
Camera model?

What camera are you using for the pictures. I looked at several and they all seem a bit large or bulky for internal cylinder pictures.
 
I believe folks are doing a bit of surgery and trimming down the neck of the dental cameras and then repairing them with heat shrink or equivalent so that they will fit the spark plug holes.

Erich
 
PeteP said:
What camera are you using for the pictures. I looked at several and they all seem a bit large or bulky for internal cylinder pictures.
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kevinh said:
Cool! Btw - I just found what seems to be the same camera from the very reputable Chinese importer 'Deal Extreme' for $70. The URL is:

http://dx.com/p/usb-2-0-4-0-mp-50x-probe-format-dental-camera-with-6-led-illumination-37296?item=4
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Looks like Kevin has found what appears to be the same one, but even cheaper! Nice going Kevin.

One note about the supplied software that I received. It really doesn't work. I found some "Freeware" on line called Debut Video Capture software. Be careful as they have a Professional version which they want money for. The free version seems to work fairly well. It's what I used to take all of these pics.


tim2542 said:
I wonder if that is corrosion on the valve that appears as red specs?
Also can you tell us how you run the engine,ie LOP or ROP?
Thanks for the info, gotta get me one of those!
Tim
Click to expand...

I am running ROP. As of late I've been trying to be more aggressive with my leaning though. ROP would probably explain why it looks like lead buildup all over the place...? Certainly could be rust I suppose... just not sure.


erich weaver said:
I believe folks are doing a bit of surgery and trimming down the neck of the dental cameras and then repairing them with heat shrink or equivalent so that they will fit the spark plug holes.

Erich
Click to expand...

Erich is correct. That's what I did (you can see it in the link to my first post). You have to be very careful with the camera after the case is cut. I thought I had broke it this weekend when removing it from one of the spark plug holes...:mad: The LED block came loose and almost fell off. A little super glue on the side and amazingly it still worked! It's pretty delicate once you cut the case apart so be careful with it.
 
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#4 Exhaust Seat Questionable

Cool pictures, the exhaust seats are showing their age. #4 appears to have low contact area, either due to pitting or deposits. Exhaust valves are cooled when they sit on the seats, between combustion cycles and with less contact for heat transfer they (it) will normalize at a higher temp. That might explain the spots, as they could be high temp corrosion, but hard to tell from the picture clarity. No idea how much life remains.

Decades ago, we mechanics would take a small coke bottle with water and dribble in the carb of car engines with lots of build up in the combustion chambers. It would clean them shiny ( like a leaking head gasket) and puke all the carbon/lead out the exhaust. It was certainly not an often used process, but quite effective. The engines ran much smoother at idle afterward due to more equal compression ratios and no pre-ingnition sources, but did nothing for valve seats or oil usage as would be expected. No engines were harmed in the process.

Maybe some guys with aviation engine experience could weigh in.
 
Scott

The red spots are normal, all is good.

Your pictures make an excellent advertisement for running LOP. ;)

Start using the APS method of climb leaning, leaning on the ground and in the cruise 10-20LOP at typically 65% or less and over the next hundred hours or so you will see things clean up.

If that was my engine I would be inclined to give it some high power and leaned into the "red box" time. For a few short bursts it will not do any damage, but it will clean it up a little.

:)
 
RV10inOz said:
Scott

The red spots are normal, all is good.

Your pictures make an excellent advertisement for running LOP. ;)

Start using the APS method of climb leaning, leaning on the ground and in the cruise 10-20LOP at typically 65% or less and over the next hundred hours or so you will see things clean up.

If that was my engine I would be inclined to give it some high power and leaned into the "red box" time. For a few short bursts it will not do any damage, but it will clean it up a little.

:)
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Thanks for the feedback David. You and Rocketbob are high on my list of engine gurus. Good to know the red spots are normal. I've not done the APS course, it's a little too rich (pardon the pun) at $1,000 for me. Even the on-line course at $400 seems a bit steep. I have to admit to being ignorant then, of how they would have one lean their engine.... All that aside I get nervous when I start leaning it out and it starts running rough. My engine is just a carbed 0320 with the good ole Bendix "Dual Mag" pack.

Just for my education what is considered the "Red Box"? I guessing I would know this if I took the APS course.

Considering most of my flying is done out of Denver normally well above 7,000 DA's. I'm sure I could be leaning a lot more. I am going to work on this... :)


rocketbob said:
Or running mogas.
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Considering how fast 100LL is climbing these days running mogas would be a nice addition. What are your thoughts on running Mogas with 9:1 compression? Everything I've read in the past says to avoid it, doesn't make them correct though. I'm sure there are lots of people out there doing it. Seems some people run one tank Mogas and the other 100LL and switch off, some mix it up. The other down side of Mogas is, it's just not available most places. I tend to fly a lot of cross country and I can recall only two or three places I've stopped which had it available...

Thanks Again,
 
O-320, great engine, pretty hard to kill too!

Rocket Bob has an excellent point. The sooner TEL vanishes from our fuel supplies the better.

G100UL is just around the corner ;) having some one on one discussions with George about the progress, I can tell you it is going well. In real terms I can't say when it will roll out, in relative terms, well it will not be too long and G100UL will be approved.

This is seriously good news for GA, sure some engines are fine on MOGAS and some strategy for dealing with it works for some folk some of the time, but getting to a point where you can roll up to the pump, anywhere, and get a certified known good aviation fuel, that is unleaded and meets everyones spec's and is not JetA, well that is simply great news for GA.

Cost of an APS course.....too cheap in my opinion. Go find me a better quality high level training course anywhere in the world that is cheaper. I am yet to find one. One graduate who was in the business of teaching people to develop and run training courses made the comment, you guys should be in my business.

The problem is your perception of value is one made from a position of naivety the old "you don't know what you don't know" syndrome, and no amount of my preaching will do it justice. You would have to just trust me. If you book in for the March course, you will get to do the online one as preparatory training for no cost. These guys do not make money out of it. I reckon every one costs GB a small fortune.

I have learned things that will not just save money, but maybe something far more valuable.

Of course it is up to you, if you want to discuss further, PM might be more suitable, rather than more thread drift.

By the way, studying valves and boroscope results is one section in the course that is very interesting indeed.;) Knowing a good one is easy, its the bad ones and how bad or urgent and why is where it gets fascinating.
 
bkilby said:
This one catches my eye.. it's got a 7MM head and is only $38 at amazon..

The dental scopes are good for looking at the valves because the camera lense is oriented at a right angle to the long axis of the instrument. While this one has a flexible extension, the camera lens looks straight out the end instead of being at 90 degress and the last few inches or so appear to be rigid. I have some concerns that you will have difficulty looking at the valves. Might be good for the cylinder walls though, which the rigid dental cameras are not. Give us a report back if you try it.

erich
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It also seems, by it's generic use, that a dental camera would be designed with a shorter focusing range and a wider viewing angle.

Some of the reviews of the borescope camera listed a few posts back would seem to bear this out.
 
One other comment about your valve seat. The contact area looks awfully wide, like the seats were not properly ground. Book says .058/.077 min/max on the seat cut. A wide seat will be less apt to clear itself of carbon or lead deposits. I do a three-way cut as I have a pretty neat tool that duplicates a Serdi valve job. Lycon and others do similar valve jobs. On most drag motors they have gone to a continuous radius with just a small flat for the valve to seat on.
 
rocketbob said:
One other comment about your valve seat. The contact area looks awfully wide, like the seats were not properly ground. Book says .058/.077 min/max on the seat cut. A wide seat will be less apt to clear itself of carbon or lead deposits. I do a three-way cut as I have a pretty neat tool that duplicates a Serdi valve job. Lycon and others do similar valve jobs. On most drag motors they have gone to a continuous radius with just a small flat for the valve to seat on.
Click to expand...


Bob,

I bought this H2AD engine used, it came out of a 172 with about 780 hours on it (the plane was getting a 360 upgrade). I have the original logbooks for the engine, which show that it was "Factory Overhauled" by Lycoming (I forget the year, sometime in the 90's) Other than me lapping the #3 Exhaust valve I would think the valve seats would be in the state that Lycoming left them after the overhaul. I have no idea what a "Standard' overhaul for Lycoming was at that point in time. Does anyone here on VAF know what Lycoming did for a "Factory Overhaul" i.e. what was replaced with new and what was tested and as long as it passed inspection re-used?
One of the things I'd like to know in particular, were the cylinders replaced with new or reworked?

Thanks,
 
"Factory Overhauled" by Lycoming ... sometime in the 90's ... were the cylinders replaced with new or reworked?
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For a factory overhaul it should have been new cylinders at the time.

Dan
 
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