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Need Help Analyzing Borescope Images - Leaking Exhaust Valve on Lycoming O-360-A2D

mtnflyr

Member
Fired up the O-360 in our RV-6A last week and it ran rough, with EGT in the #3 cylinder failing to come up. Shut down the engine and pulled the plugs - they looked find. Then, a compression test and we could clearly hear air entering the exhaust system. Bought an inexpensive borescope, and the following are video clips and images of the exhaust valve in question. I've not analyzed borescope imagery before and could use some help with what these show. I'm reading everything I can find on leaky exhaust valves and ordered a valve guide reamer from McFarlane in case this is a stuck valve. I'm also looking into lapping the valve in place since it appears to me (remember I've never done this before) that there is significant pitting on the valve and the seat.

Help!

youtu.be/D9OgOrHm-xg
youtu.be/5etTaez_qoA

IMG_0001.JPG

IMG_0002.JPG

IMG_0003.JPG

IMG_0004.JPG

IMG_0007.JPG

IMG_0009.JPG
 
I've had mixed success with in-situ valve lapping. Sometimes its just better to pull the cylinder and have a new guide installed and clean up the valve and the seat. You will have to check the dry tappet clearance if this is done when you put the rockers and pushrods back on.
 
Ok, my 2ct...
we could clearly hear air entering the exhaust system
This could basically mean 2 things: either a stuck valve, or a leak around the seat... which doesn’t automatically result in a non firing cylinder.
Looking at vids & pics, the valve can be rotated easily, thereby discounting the guide/stuck valve theory.
Valve seat, I don’t see a specific spot, which would show as a black trail, on either the seat nor the seat. The valve burn image shows a quite regular pattern of an engine with a couple of hundred hours, not fully concentric, but regular pizza.

So my quick glance doesn’t reveal any obvious defect. Stupid question, is the «*air entering the exhaust*» happening on cylinder #3?
What were the values of the compressions?
 
Looks good

Agree with Dan, looks great to me. Compression test, hot or cold? Numbers? Running rough, did you throttle up and try to clear? Any chance your compression testing was flawed.
 
Nice images. What borescope did you use?

https://www.amazon.com/gp/product/B086X1XGN1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Not sure I'd recommend it. The first one I received wouldn't hold a charge. I returned it to Amazon and they sent me a new borescope and this one won't charge past halfway and runs out of juice in around 30 minutes. It's also a chore to get it oriented correctly - bend, install, pull it out, bend it again, hold your tongue just so . . . . If I return this borescope, I think I'll go with one of the Vividia products. The VA-400 is recommended by Mike Busch and it was after watching his AOPA presentation on exhaust valves that I bought this unit. I think the ability to bend the head from outside the cylinder would make this job a whole lot easier.
 
Agree with Dan, looks great to me. Compression test, hot or cold? Numbers? Running rough, did you throttle up and try to clear? Any chance your compression testing was flawed.

Ran the engine long enough for the EGTs to come up and #3 was hardly rising at all. Very rough. Compression test the next day, cold. 30/80 in #3. Very obvious air sound in the exhaust pipe. Definitely leaking.

I'd been getting a "pop, pop, pop" at full throttle on climb out for a couple of flights earlier, and that concerned me. Running a bit rough, but everything smoothed out once she warmed up.

Funny thing is, before that the engine had been running the smoothest it has since we bought the airplane and the compression tests were the highest and most consistent ever at this year's annual done last month (78/80).

Sent the pics to a cylinder shop and they said the pitting was consistent with a mid/high time engine. They recommended trying to lap in place and when that didn't work, pull the jug and send it to them. They said to expect the lapping in place wouldn't fix the issue.
 
I've lapped a number of valves in place on my 0-360 which on average raised each cyl about 15lbs. I did this over a 2 year period but it would always start leaking again. We pulled the Cyl's and found very worn valve guides on the exhaust valves.
 
I've lapped a number of valves in place on my 0-360 which on average raised each cyl about 15lbs. I did this over a 2 year period but it would always start leaking again. We pulled the Cyl's and found very worn valve guides on the exhaust valves.

I think that's the next step for this valve. Worth a try as it doesn't cost me more than the price of some lapping compound. Couple of questions:

- What lapping compound did you use?
- I'm worried about getting the grit on the cylinder walls and the valve stem. How did you get things cleaned up in between changing grits and when you were all done?
- How hard do you pull on the valve stem? Is this just a light pull, or lots of pressure?
- Thinking of making a jig to hold my dial indicator to do a wobble test. Did you do that?
 
- What lapping compound did you use?
- I'm worried about getting the grit on the cylinder walls and the valve stem. How did you get things cleaned up in between changing grits and when you were all done?
- How hard do you pull on the valve stem? Is this just a light pull, or lots of pressure?
- Thinking of making a jig to hold my dial indicator to do a wobble test. Did you do that?

I just used permatex valve lapping compound from the auto parts store. 2 grits
We sprayed the valve with brake cleaner through the spark plug hole with the lower plug out to drain the excess out.
Pull as hard as you can while spinning it.
I didn't do the wobble test (looks like I should have as that's where mine failed in the end)
 
For $90 it might be worth transplanting the camera to the 180deg head of the (my) VA400.

My Teslong borescope for .22 cal bores has excellent resolution.
 
Looking at it now, I’d also try the lapping.
The wobble test would be an indicator of the guide’s condition, values published in SB388C, probably 0.30 for your engine. The SB also states If valve stem movement is in excess of the maximum limit listed in the table, the valve and guide must be replaced.
 
More is expected.

I take it you aren’t happy with the VA-400 resolution.

Clearly - - the mark-1's have been inspecting internal engine parts for 50 yrs and this just falls short of desired. Still quite useful, and the articulation is really needed, but since low cost CMOS with proper focal range is available at a reasonable cost it seems reasonable to expect more. Reasonable? Two much?:D

If Teslong made one that articulated, based on their other products I have seen, it would be 3-10X the resolution and same cost.

To the OP - as stated, wobble test is recommended - read the SB closely - likely .015 or greater is recommended. .030 is the limit (likely). You can spin the valve an get a better view of the seat with the valve sitting in the bore. If it looked nice and even there . . . Honestly, I would not lap until it had been checked and run for 5 hrs or so at cruise (not in the pattern). That's just me, and it's not that much time to de-cowl and get it back apart.

I recently helped TTHrew do a wobble test and hone, It was not difficult at all. There is a very good YT tutorial on the process that relocates the valve to the bottom of the cylinder then pulls it back into the guide, 15 seconds is all it took for that step. A strong magnet through the guide, good light, and snap-on two prong mechanical finger ($22). Do make a little hook from 0.040 safety wire to handle the valve through the upper plug hole an it can be viewed through the upper plug hole all the while. Following rocketbob's advice on the hone, it worked nicely.

Here is a David Clark short clip on his wobble fixture. YMMV but the valve did not exhibit a clear burning in some region, it looked even all around. Was the valve tight when you rotated it? Did you remove the the spring to make the video? Tell us more to determine if it is just a sticky valve with a tight guide.
 
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Did you remove the the spring to make the video?
:D

Apologies for the thread drift:
VA-880 borescope Mickey... tested yesterday to inspect some tank installation on a T-51 Mustang project. Very happy, yet to test on an engine.
 
Vividia quietly updated the VA-400 scope to a higher resolution - and also updated the price accordingly.
 
Here is a David Clark short clip on his wobble fixture. YMMV but the valve did not exhibit a clear burning in some region, it looked even all around. Was the valve tight when you rotated it? Did you remove the the spring to make the video? Tell us more to determine if it is just a sticky valve with a tight guide.

I did remove the valve spring to check the valve guide and push the valve in enough to get a good look at the seat. The valve moves freely in the guide with very little wobble. I'm making a wobble test fixture today and will measure that according to the Lycoming Service Bulletin 338C just to make sure I have a good guide.

Based on the responses, I'm planning to give the lap-in-place procedure a try. Seems like nothing to lose there and it just might fix the leak - at least temporarily. I'll post images of the result.

I have the custom exhaust valve guide reamer from McFarlane showing up today and plan on running that down the guide if the wobble test shows a tight clearance. They don't give those reamers away . . .

I haven't seen any comments on cleaning the base of the valve stem. That seems like the place where lead deposits would lead to a sticky valve. Since I'm messing around in there, I'd like to clean that part of the valve. Any recommendations on what to use? Purple Scotch-Brite?
 
mtnflyr, with all due respect, it looks like you know what you're doing and talking about ;)

On my side I have some dozen of years of experience in aviation and engines, but maybe one of the more experienced engine expert wants to chime in?

In the meantime... I concede being baffled some by your problem.
The sound of air in the exhaust identifies the exhaust valve as being the culprit. Now this valve looks ok to me, in that the circumference of the mating surface is evenly shiny, meaning the rotator cap is doing its work.
The valve seat also looks ok. One can get uneven wear on those if they are slightly canted, or loose. Signs would be black "soot" marks either blueish or black, or black powder around the seat. Nothing like this visible.
Now a 30/80 is quite some drop, and I'm surprised not seeing any direct and visible reason for that.
The valve being freely moveable probably means that the guide is ok, e.g. none of this sticking valve business.

Re cleaning the valve stem: I've used Scotch-Brite in the past, not the purple, but the gray which is somewhat softer.
Also I wouldn't worry too much about either Scotch-Brite or lapping compound leftovers. Of course remove as much as possible (long Q-tips dipped in alcohol are quite handy for the valve/seat) of the residues, but: In an engine running at say 1000RPM, the exhaust valve will expel the hot gases and any residue down the pipe 250 times a minute or 4.1 times per second, quick cleaning is guaranteed ;)

Looking forward to your feedback, thanks.
 
Had a friend with a similar scenario, turned out that the seat was slightly loose in the head and leaking AROUND the seat and out the exhaust.
 
Results

Thanks for all the help and recommendations. We decided to lap the valve in place and ream the guide after the wobble test showed .010” movement in the valve stem. Managed to drop the valve into the cylinder when the tenuous grip the mechanical fingers had on the valve stem slipped. If that hadn’t happened, this would have been an easy fix. Per Murphy’s Law, the valve ended up with the stem facing the piston and it took some fiddling with mechanical fingers and a pick to get it turned around and inserted back in the guide.

The reamer cleaned out a fair amount of black deposits. Not sure what the root cause for the leak was, but the guide was much more gummed up at the end toward the seat with the last 1/2” harder to ream.

We wiped the valve and seat carefully after lapping and used one of those venturi-suction air guns to blow a mist of solvent into the cylinder that drained out the lower spark plug hole with the left side of the airplane jacked up to make sure we didn’t leave any grit inside. Used the same gun to fog the cylinder with engine oil to make sure we didn’t score the cylinder walls with a dry startup.

After reassembly, the motor fired right up and the #3 EGT spiked higher than the rest of the cylinders for a minute or two as the excess oil burned off, then things settled down nicely. Back to a smooth-running engine - at least for now.

I’ll add borescope images of the lapped valve later - cleaned up nicely.
 
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Standard Procedure.

Glad the process went well Rick. But - -positioning the valve inside the cylinder is part of the best-in-class process. The process is to have a hook made for the valve to hold the heavy end so when it is pushed inside it does not drop and ding the cylinder wall. Then use a powerful telescopic magnet to grab the end and pull it back through the guid with the hook holding it up for insertion alignment. A nice light inside the lower plug hole will illuminate the interior so all is easily seen from the upper hole.

For more loose guides, some fine dental floss can be wrapped on the end of the valve to hold it after it is pushed in, but I found the tight guide shears it off and after using the magnet&hook method would not recommend it as standard.

To be honest, this process was counter intuitive to me until I tried it. The two finger snap-on mechanical finger tool is recommended (required) - $21.75. The 4 finger tools will not capture the 1/2" valve stem firmly as needed.

To your guide - it is normal for the tight area to be on the hot end, heat is what causes the collection of material on the guide as lubricant flows down from the rocker box. Basic engine 101.
 
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Glad the process went well Rick. But - -positioning the valve inside the cylinder is part of the best-in-class process. The process is to have a hook made for the valve to hold the heavy end so when it is pushed inside it does not drop and ding the cylinder wall. Then use a powerful telescopic magnet to grab the end and pull it back through the guid with the hook holding it up for insertion alignment. A nice light inside the lower plug hole will illuminate the interior so all is easily seen from the upper hole.

For more loose guides, some fine dental floss can be wrapped on the end of the valve to hold it after it is pushed in, but I found the tight guide shears it off and after using the magnet&hook method would not recommend it as standard.

To be honest, this process was counter intuitive to me until I tried it. The two finger snap-on mechanical finger tool is recommended (required) - $21.75. The 4 finger tools will not capture the 1/2" valve stem firmly as needed.

To your guide - it is normal for the tight area to be on the hot end, heat is what causes the collection of material on the guide as lubricant flows down from the rocker box. Basic engine 101.

Yeah. This was a learning experience. I can attest that the 4 finger tool doesn't grip the stem firmly enough. Next time I'll have the right gripper:

https://shop.snapon.com/product/Claws-(Flexible)/Flexible-Pick-up-Tool-(Blue-Point)/GA265A

and tie some thin string on the stem around where the keepers seat so I can gently drop the valve into the cylinder. I think I can get the string around the stem once it is pushed out of the guide and the gripper is holding it in the exhaust port. I needed to get the valve all the way out of the way to make room for the pilot on the McFarlane reamer to clear the guide. Once the stem was back in the exhaust port it was pretty easy to slide it into the guide using a gripper on the stem in the port and a pick with a 60 degree bend at the end inserted through the upper spark plug hole. The pick let me lift the heavy end to line up the stem with the guide and it slid right in.
 
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Images of the lapped valve and some of the tools I made to do t the job

After lapping the valve. I was pleasantly surprised how easily the pitting cleaned up.

20210605_Lapped%20Exhaust%20Valve%20%233%20Cylinder%202.JPG


My shop-made wobble test fixture and stem extender. The wobble test fixture holds the dial indicator the prescribed 1.19" from the machined head face and the extender allows for measuring stem movement at that point.

Exhaust%20Valve%20Wobble%20Test%20Fixture.JPG


Valve%20Stem%20Extender.JPG


Valve spring compressor. I didn't want to use the lever type compressor sold for this purpose, and this plate mounts on the valve cover screw holes with the nuts on the bolt letting you compress the spring and hold it there while you dig the keepers out.

Valve%20Spring%20Compressor.JPG
 
To your guide - it is normal for the tight area to be on the hot end, heat is what causes the collection of material on the guide as lubricant flows down from the rocker box. Basic engine 101.

Interestingly, that's not all that happens with Lycoming engines, according to Mike Busch. I found this presentation while researching my issue:

https://www.youtube.com/watch?v=7ohsVvYbAaQ

And this opinion piece by Mike in AOPA Pilot:

https://resources.savvyaviation.com/wp-content/uploads/articles_aopa/AOPA_2020-07_why-valves-stick.pdf

Skip ahead to 11:00 in the presentation where he talks about Lycoming engines that run low CHTs experience more valve sticking than those that run hotter - counter to what would be expected if the mechanism is oil in the guide coking the guide. There's a bunch of information on why Lycomings experience valve sticking much more often than Continentals and it's due to the sodium-filled Lycoming valves running cooler in a range that the lead in 100LL gasoline condenses on the stem and guide. It's lead that's causing the valve sticking, not carbonized oil, according to analysis done by Lycoming. As a result, you'll see the recommendations in SB 338C for testing and in SI 1425A for reaming at 400 hours for Lycomings and no similar recommendations for Continental engines.

This rang true for my engine as we experience low CHTs (which I thought was great until I listened to Mike's presentation). I think the hiccup we saw on startup with the engine running rough and EGT not coming up might have been early "Morning Sickness" - evidence that the #3 exhaust valve was just starting to bind up. The wobble test showed a tight guide, although I don't know how tight the wobble test needs to be to have a stuck valve. My guess is I didn't need to lap the valve, but I don't think that hurt anything.

In retrospect, I kinda wish I'd lapped the valve, then fired it up to see what that did before reaming the guide. Because I did both at the same time, I'll never know which fixed the problem. I was eager to get the plane back in the air . . .
 
happy to learn all is good now mtnflyr.

The process is to have a hook made for the valve to hold the heavy end so when it is pushed inside it does not drop and ding the cylinder wall. Then use a powerful telescopic magnet to grab the end and pull it back through the guid with the hook holding it up for insertion alignment.

Yep, Bill is using the same technique I did on a few occasions, works pretty good. Performed the SB on my O-360 last year, took about 3 hours to measure, or wobble test, all 4 cylinders.

I’ve had my share of blocked valves, on small bore Continentals, and Lycomings. But on none of them was I able to freely spin the valve as you could... as a matter of fact, on the two last ones on a O-320, I had to heavily hammer the valve in :eek: Telltale was heavy morning sickness, clearing itself after a couple of minutes warmup time...

May your cylinder be happy for many hours to come.
 
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Thanks for posting pictures of your homemade tools. They look good. It would be even cooler to have a couple of pictures of them installed/mounted on the cylinder so we can visualize how they work if we haven't done this ourselves before.

After lapping the valve. I was pleasantly surprised how easily the pitting cleaned up.

20210605_Lapped%20Exhaust%20Valve%20%233%20Cylinder%202.JPG


My shop-made wobble test fixture and stem extender. The wobble test fixture holds the dial indicator the prescribed 1.19" from the machined head face and the extender allows for measuring stem movement at that point.

Exhaust%20Valve%20Wobble%20Test%20Fixture.JPG


Valve%20Stem%20Extender.JPG


Valve spring compressor. I didn't want to use the lever type compressor sold for this purpose, and this plate mounts on the valve cover screw holes with the nuts on the bolt letting you compress the spring and hold it there while you dig the keepers out.

Valve%20Spring%20Compressor.JPG
 
Interestingly, that's not all that happens with Lycoming engines, according to Mike Busch.

Interesting information, but linking solely to the CHT is a bit of a handwaving stretch. Valve temps are mostly a function of the exhaust gas temperatures. There was a detailed research project on this in the NACA archives confirming that. The heat transfer and surface temperatures at the sliding interface of the end of the valve is certainly quite important, but to generalize about that from CHT is where the argument falls short of data.

I like the fuel fouling aspect as we know that it is not all oil and and oversimplification on my part. But, it is a fact that both will occur where the end of the exhaust valve is exposed when open the pulled back in to the guide area. That area is treated in design in different ways, some being a relief in diameter of the last portion of the guide to shield that length somewhat from deposits. Having rebuilt a couple of hundred auto engines and lived in the diesel/gas engine development world for decades, the bottom length of the guide is the most challenging and it can either wear excessively or seize up. Most engines have the wear issue then extend the length of the valve and port and do the shielding - - all factors challenged in the short overhead geometry of the opposed cylinder, aircraft design with limited lateral distance. Diesels can use a longer thin stems and port design to address deposits. They won't have direct acting rocker arms and only have linear forces (and action) for opening. I say diesels but they are typically also designed to function with gaseous fuels - landfill, propane, methane etc. Again, all compromise (balance) the design for the weight, life, cost of the specific application.

I like the tools, well done. Until doing one of these wobble/ream procedures, I did not realize that the lever spring removal is not ideal. A linear tool, like you made, is better for work flow.

That thermal plot of the exhaust valves (in the video) is interesting and greatly helps the communication of the situation! You did some excellent research.
 
Busch FEVA

I subscribe to Savvy, they run all uploads through their Failing Exhaust Valve Analysis/FEVA, looking for signs of pending EV failure. Per their analysis, a pending EV failure will have one anomaly of rapid EGT fluctuations/oscillation. I believe they have found 60 cases of this , further investigation indeed show pending/ imminent EV failure.
 
Interesting information, but linking solely to the CHT is a bit of a handwaving stretch. Valve temps are mostly a function of the exhaust gas temperatures. There was a detailed research project on this in the NACA archives confirming that. The heat transfer and surface temperatures at the sliding interface of the end of the valve is certainly quite important, but to generalize about that from CHT is where the argument falls short of data.

I like the fuel fouling aspect as we know that it is not all oil and and oversimplification on my part. But, it is a fact that both will occur where the end of the exhaust valve is exposed when open the pulled back in to the guide area. That area is treated in design in different ways, some being a relief in diameter of the last portion of the guide to shield that length somewhat from deposits. Having rebuilt a couple of hundred auto engines and lived in the diesel/gas engine development world for decades, the bottom length of the guide is the most challenging and it can either wear excessively or seize up. Most engines have the wear issue then extend the length of the valve and port and do the shielding - - all factors challenged in the short overhead geometry of the opposed cylinder, aircraft design with limited lateral distance. Diesels can use a longer thin stems and port design to address deposits. They won't have direct acting rocker arms and only have linear forces (and action) for opening. I say diesels but they are typically also designed to function with gaseous fuels - landfill, propane, methane etc. Again, all compromise (balance) the design for the weight, life, cost of the specific application.

I like the tools, well done. Until doing one of these wobble/ream procedures, I did not realize that the lever spring removal is not ideal. A linear tool, like you made, is better for work flow.

That thermal plot of the exhaust valves (in the video) is interesting and greatly helps the communication of the situation! You did some excellent research.

I'm not convinced by the low CHT theory either, but I am actively running the experiment. My CHTs range from 240--290F on my angle-valve engine. After 600+ hrs, the exhaust valve stems look pretty darn clean. Of course I run very LOP. I also lean as I climb to maintain the same EGT that I have at take-off, and once MAP drops below 25", I lean to 50--75 ROP for the remainder of the climb. So I am keeping EGTs fairly high for the time I am running ROP. All these factors present less available lead to precipitate out.

I also don't buy the lead build-up story. I've scraped clean many an exhaust valve, and it seems to me the build-up is a combination of coked oil and lead. I have a hypothesis that if the valve is cool enough that the oil doesn't coke on it, then the liquid oil film from each cycle of the valve might receive a deposit of lead precipitate, which is then wiped clean by the next upstroke of the valve. So it doesn't build up. Given that Lycomings seem to have rather poor valve stem oiling, this may be non-sense...we'll see......
 
Thanks for posting pictures of your homemade tools. They look good. It would be even cooler to have a couple of pictures of them installed/mounted on the cylinder so we can visualize how they work if we haven't done this ourselves before.

I got caught up doing the work and didn't think about taking pictures. I still have to wobble test the other three exhaust valves, so I may remember to take pictures of the tools mounted on the cylinders. I'm a cheap Yankee by upbringing and make a lot of my tools and fixtures rather than buying them. Often they function better than what you can buy . . . and I learn a lot in the toolmaking process.
 
This was an interesting video:

https://www.youtube.com/watch?v=71cMqxZtgAs

Might come in handy some day...

Saw this and almost every video Mike/Savvy has on YouTube. I'm a big advocate of learning all you can from people who know best. Mike B is a blessing to us in the EAB community. As much as he helps the certified guys get through maintenance issues with the best possible outcome at a reasonable price, he really brings a lot of value to us, since we can do our own work.
 
https://www.amazon.com/gp/product/B086X1XGN1/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

Not sure I'd recommend it. The first one I received wouldn't hold a charge. I returned it to Amazon and they sent me a new borescope and this one won't charge past halfway and runs out of juice in around 30 minutes. It's also a chore to get it oriented correctly - bend, install, pull it out, bend it again, hold your tongue just so . . . . If I return this borescope, I think I'll go with one of the Vividia products. The VA-400 is recommended by Mike Busch and it was after watching his AOPA presentation on exhaust valves that I bought this unit. I think the ability to bend the head from outside the cylinder would make this job a whole lot easier.

I can highly recommend Vividia VA-400.
 
Fired up the O-360 in our RV-6A last week and it ran rough, with EGT in the #3 cylinder failing to come up. Shut down the engine and pulled the plugs - they looked find. Then, a compression test and we could clearly hear air entering the exhaust system. Bought an inexpensive borescope, and the following are video clips and images of the exhaust valve in question. I've not analyzed borescope imagery before and could use some help with what these show. I'm reading everything I can find on leaky exhaust valves and ordered a valve guide reamer from McFarlane in case this is a stuck valve. I'm also looking into lapping the valve in place since it appears to me (remember I've never done this before) that there is significant pitting on the valve and the seat.

Help!

youtu.be/D9OgOrHm-xg
youtu.be/5etTaez_qoA

IMG_0001.JPG

IMG_0002.JPG

IMG_0003.JPG

IMG_0004.JPG

IMG_0007.JPG

IMG_0009.JPG

Am I the only one that can see the lead ball in the spark plug in image #4. That could cause a rough runing engine.
 
I can highly recommend Vividia VA-400.

I no longer recommend purchasing the Vivida VA-400 due to worse-than-poor customer support. I had the older lower resolution VA-400L (still works), and bought their newer HD VA-400L direct from Vividia (at Airventure). It quits after 5-30 minutes of operation. The lights go off, the device is no longer seen by the computer (repeatable on mulitple laptops). Vividia does not respond to customer support requests AT ALL. Not to email requests, not to requests to their repair web site.

Since Vivida won't stand behind their product, I'm looking at other articulating borescopes from Amazon. I see some promising ideas in this thread: https://vansairforce.net/community/showthread.php?t=192632&highlight=borescope&page=3
 
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