Valve borescope image help

I have an IO 360A1B6 with about 500 hours SMOH. I bought a USB dental camera to take a look at my valves. All of my exhaust valves looked normal according to the Air Safety Institute valve image guide. They all had concentric patterns, minor deposits and no green or semi circles. However I was surprised to see this pattern on my intake valve on #2 and #4. The image shows a darker area directly across from the exhaust valve. It does not seem to me to be serious but I am looking for opinions/advice. Intake valves in #1 & #3 did not show this pattern. My apologies for image quality, I took a photo of my computer video.


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Can you be more specific?
What exactly is your concern and where exactly?
Shadows and image degradation can play a lot of tricks on you, and us.

Sorry for the image quality. The lower photo is a closeup of the upper one. I am adding another image from the intake valve of another cylinder. It appears that it is a very thin silver colored coating that is gradually flaking off of the surface of the valve. I also noticed it on the valve seat. There does not appear to be any heat signatures, but it is occurring directly across from the exhaust valves in #2 and #4. To complicate matters I also notice the same pattern to a lesser degree on the opposite side of the intake valve in #4.

I have read that exhaust valves are designed to rotate during normal operation. Do intake valves do this also? I have also heard that when the lifter/cam starts to wear the valve will no longer rotate and this leads to increased stress on the valve.

My oil analysis has been normal to this point. I will be sending in the latest sample today.

I have added another image that may illustrate the "flaking effect" that I detect.

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I'll try

I hope others will also give it a shot .
I have been taking every opportunity to look at mine and other people's cylinders and valves and educate myself on these matters.
So, I am not and expert but one day I'll be one.

First off, I don't think you have an issue.
It appears to me that the valve pictured shows carbon build up on part of it and a fairly clean "black" portion on the rest of it.
The valves are supposed to rotate and why some of the valve face shows carbon and some it it does not is unclear to me but I see it quite often.
Keep in mind that a greatly enhanced or magnified picture like those from a dental camera can reveal things that you cannot otherwise see.
With good compression and no other issues on EGTs and especially CHTs
you should not be concerned.
I do hope others with more experience looking at valves will contribute or even dispute what I have said.

That is perfectly normal.

Relax.


Insert tongue in cheek?...
If you want to get all the flaking affect to go away, run filthy rich all day long (do not do that) or run around at sea level and about 35-50dF ROP (again do not do that). Then you will have heavy deposits or none at all.

All looks good.

Those look like additive deposits. I only have real experience with auto engines, but today's auto gas will leave whitish or tanish deposits on the intake valves and are not carbon. I don't know what they put in 100LL, but I assume some of the same additives are used.

Larry

The picture quality leaves a lot to be desired. Are there any deposits/ build up on the head, piston and valve face? In the pictures, it appears that these items are pretty much void of any deposits and that you are almost looking at bare metal with very light or no build up at all and a shinny bare metal appearance. If that is the case, metal with very little or no deposit build up, would be extremely unusual for a 500 hour engine and indicative of a lot of heat in the combustion area. The excess heat kinds acts like a self cleaning oven and burns all the deposits off leaving the head, valves and piston very clean in appearance. IMHO, that type of appearance is not normal for a 500 hour engine and the source for the heat should be investigated. Maybe I am misinterpreting the pictures but the items in question look way to clean to me.
Good Luck,
Mahlon

Mahlon, in a heavily ROP run engine you would be correct. For a ROP climber and LOP cruiser, that is quite normal and healthy.

RV10inOz said:

Mahlon, in a heavily ROP run engine you would be correct. For a ROP climber and LOP cruiser, that is quite normal and healthy.

Click to expand...

I am not sure that I agree with this statement. I have torn down several automotive engines and never see one this is "clean" of deposits. They all spend most of their time running what I would call lean. While in the auto world we don't use EGT, I am comfortable that the 14.7:1 AF ratio that these engines run at resides lean of Peak EGT. There is always a light coating of deposits on metal. Not traditional carbon deposits. This is especially true on valves.

I agree with Mahlon that bright shiny metal is something worthy of investigation.

Larry

I was surprised by how clean the heads and valves appeared also. I do aggressively lean on the ground, and once at cruise below 75% I typically run just LOP. I wish my camera would take stills, but it only shoots video and my files are too large to upload. Therefore my poor image quality is due to a camera phone image of my paused video on my computer. I have my annual coming up in December and I will have my A&P look at the videos. Thanks all for your input.

Larry, in the world of Avgas burners, this is clean and the flaky deposits come off like that normally.

If you don't believe me thats fine, but I would suggest you go ask a guy like George Braly about them. I reckon he has seen more than his fair share but not only that he actually understands what he is looking at. There is a difference.

PS: (please do not do that, he is far to busy working on unleaded avgas to be bombarded by questions like this).

Just a followup to my original post. I recently viewed Mike Busch's Savvy Airplane Mx "All about Cylinders". His webinar if full of pictures of both normal and defective valves and cylinders. He presented several pictures of healthy valves that have the mottled appearance that concerned me. I am still going to show the video to my IA at the annual, however I am confident that my valves/cylinders are in good shape. I realize that I have the benefit of seeing the entire video and I could only share a few pics with the forum but I do appreciate the inputs.

I viewed Mike Busch's webinar a few days ago coincidentally, and my thought reading this thread was that your pics look good -like the good ones Mike shows. I'll also add that he does offer to review peoples pics on his Savvy site if you send them, though you would want to verify that.