#3 at your red 3. See the edge, darken, could be hotter in that location? Other than lack of likeness to each other, they seem symmetrical in the patterns on all. Guessing you run rich of peak . I run UL 93 , 99% of time, so this comment is based on how mine look no lead. My amateur analysis , butI have looked at a lot borescope pictures. Here is my #3 recently, with black spot starting too. I lapped in place 10 hours ago, no look since.
They all have the expected 'burned pizza' look except for the 4th photo. Interesting central deposit! I would take another picture of #3 with the valve open to see what the valve and seat face look like at that darker spot.
that is interesting. I saw the same lack of rings and other artifacts on #4 and assumed that valve was running too cold. I wasn't really sure of my analysis, so deleted the message. I assumed the sticking lead or aluminum deposits were due to a cold valve and not a hot one. Also, the lack of heat signature on the seat tipped me that way. Also, if the valve was getting excessively hot, I would have expected there would be some asymmetry where there was some heat transfer to the seat.
good looking pizza!
Need to see all edges , otherwise looks normal
Funny! Mine look similar to yours but with extra cheese.
Myth, no relation, or very little, on that. My carbed O-360 runs LOP (on all cylinders) everyday, but the "secret" is in the electronic ignition.
Mike, are rotating valves a good thing, or a not so good thing?
Imagine a flat hammer slamming down on a ring. The trauma of a valve closing is such that any deposit from a valve surface or piston surface that gets between a valve and the seat will be gone before you can say Pass the peas! Poof!
Huh,,,,,,,,,, Maybe "slamming" was the wrong word. Quickly closing so as to get quickly shut before the explosion of the fire wave crosses the piston. It is not a gentle thing but perhaps not slamming. Wrong choice of words but the point: closing of the valves is not going to be hampered by a bit of deposit on the face of the valve. Poof. When you hear a radial engine winding down after shutdown, part of the loud clattering you hear are the valves gently closing. Quickly.
Well, these replies are GOLD. The most obvious one that escaped me, was the closeup nature. OF COURSE. What I saw as scary boulder size chunks of lead are now much easier to look at without my credit card twitching in my pocket.Huh,,,,,,,,,, Maybe "slamming" was the wrong word. Quickly closing so as to get quickly shut before the explosion of the fire wave crosses the piston. It is not a gentle thing but perhaps not slamming. Wrong choice of words but the point: closing of the valves is not going to be hampered by a bit of deposit on the face of the valve. Poof. When you hear a radial engine winding down after shutdown, part of the loud clattering you hear are the valves gently closing. Quickly.
Exhaust valves are designed to rotate, and this rotation is essential to valve longevity since it helps prevent deposits from building up around the seat, stem, and guide.
Thanks Mike... good stuff to know.
