Exhaust valve - burnt or not?

[DXB]

Can't decide what to make of my #4 exhaust valve on borescope:

In the pic, deposits at the outer rim are heavy from 9-12 o'clock, lighter from 12-4 o'clock, very light from 4-9 o'clock.   No obvious crescent at the edge, but in I've found changes that seemed subtle on borescope view of exhaust valve faces to be clear as day after pulling a cylinder to examine directly. 

O-360-A1D 1300 SMOH with Millenium cylinders, and this is the only one of the four cylinders that hasn't been IRAN'd or replaced yet.  When pulling prop through the compression stroke on this cylinder, it's not obviously soft, and there's no audible hiss at the tail pipe (poor man's compression test).  There's no imminent valve failure signature upon looking at the EGT trace on the SAVVY website. 

I'm thinking just watch it for now unless folks think otherwise.  Annual is in 2 months, and I'm just starting to make my list of stuff to get done...

 

 

[Rwsavory]

I’m not an expert, but that doesn’t look burnt to me. Here’s a picture of one of my exhaust valves from about a couple years ago.  It got replaced. 

[EricJ]

2 hours ago, Rwsavory said:

I’m not an expert, but that doesn’t look burnt to me. Here’s a picture of one of my exhaust valves from about a couple years ago.  It got replaced. 

The green crescent on the bottom is the problem.   If you have that, it needs attention.

[DXB]

6 hours ago, pmccand said:

Compression test.  If normal, leave it alone and go fly.

 

Certainly a burnt valve can pass a static compression test, underscoring the value of the borescope exam - the valve may not be so close to failure as to be an urgent issue, but annual is a good time to address the problem regardless.  Unfortunately I've seen a couple of valves that were clearly burnt upon pulling a cylinder but were not nearly as apparent on borescope as the classic green crescent appearance shown by @Rwsavory - hence my second guessing here.

[N201MKTurbo]

You should look at the valve seat with the valve open. You can see the sealing surface. If it is continuous all the way around on both the valve and the seat, you are OK.

Admittedly, it is hard to see the whole thing some times, but if it is bad, you can usually tell.

[slowflyin]

Valve looks normal to me.   I'd run it and recheck.

[carusoam]

Dev,

The pizza image looks nice and uniform, no edge effects...

The build up around the seat, may be saying something... let’s see a comparison...

Do you have pics of the other three?

PP thoughts only, not a mechanic...

Best regards,

-a-

[DXB]

9 hours ago, carusoam said:

Dev,

The pizza image looks nice and uniform, no edge effects...

The build up around the seat, may be saying something... let’s see a comparison...

Do you have pics of the other three?

PP thoughts only, not a mechanic...

Best regards,

-a-

I think the photo underestimates the asymmetry visible at the edge while looking at the dynamic video - I think it's probably fine vs. at the earliest point in the process of destruction to address.  I didn't snap a pic of the other 3 because they raised no concern at all.  Agree it's probably a good idea to do so for long term comparisons though, like I will do for #4.

[PT20J]

Maybe this will help:

14FN0000-ASI-Valve-Safey-Poster_Final.pdf