ChuckGant
Well Known Member
Looking for input on the looks of these exhaust valves. They are from a Lycoming O-360. Really curious about the deposits and wonder if there is anything to be concerned about.
Thanks,
Chuck
Thanks,
Chuck
#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.Looking for input on the looks of these exhaust valves. They are from a Lycoming O-360. Really curious about the deposits and wonder if there is anything to be concerned about.
Thanks,
Chuck
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.Looking for input on the looks of these exhaust valves. They are from a Lycoming O-360. Really curious about the deposits and wonder if there is anything to be concerned about.
Thanks,
Chuck
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.9398 (4) looks like it is way to hot but it is even - - might not stay that way long. How are leak-down tests? Do you have an intake leak on this one? Could be sticking and not seating well, allowing it to get hot.
The rest don't have any concerning lack of symmetry, but look like the engine does't get run at cruise often.
Definitely more detailed inspection for #4
good looking pizza!Well, having looked inside my O-320 yesterday, I am jealous of yours. Mine look like an aerial view of a junkyard. At 900 smoh, I am wondering what the veteran bore scopers think about this valve??????
Need to see all edges , otherwise looks normalWell, having looked inside my O-320 yesterday, I am jealous of yours. Mine look like an aerial view of a junkyard. At 900 smoh, I am wondering what the veteran bore scopers think about this valve??????
Funny! Mine look similar to yours but with extra cheese.Well, having looked inside my O-320 yesterday, I am jealous of yours. Mine look like an aerial view of a junkyard. At 900 smoh, I am wondering what the veteran bore scopers think about this valve??????
I plan to fly it for another 25 hours and borescope it again on the next oil change
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.It is carbureted, so we can't run lean of peak
Mike, are rotating valves a good thing, or a not so good thing?Lead oxide deposits, due to overly rich mixture. Lean aggressively especially on ground and learn proper leaning procedures in flight.
the deposits won’t hurt the valves, edges look fine. You have concentric deposits indicating the valves are rotating.
Lead oxide deposits, due to overly rich mixture. Lean aggressively especially on ground and learn proper leaning procedures in flight.
the deposits won’t hurt the valves, edges look fine. You have concentric deposits indicating the valves are rotating
Continental engine's have a history of not rotating more often than lycoming . Yes they all should rotate.Mike, are rotating valves a good thing, or a not so good thing?
Second question: do the lead deposits around the perimeter of valves tend to stay stuck in place? Some look large enough to really block a valve open if they came unstuck and got swallowed.
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!Second question: do the lead deposits around the perimeter of valves tend to stay stuck in place? Some look large enough to really block a valve open if they came unstuck and got swallowed.
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.If your valves are “slamming”, then something is wrong.. valves don’t slam shut. They have opening and closing ramps built into the cam lobes. If they slam, then they’ll pound out the seats, break or bend valvetrain parts, ect…
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.Mike, are rotating valves a good thing, or a not so good thing?
Thanks Mike... good stuff to know.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.
This engine is on a Cessna 172. It is carbureted, so we can't run lean of peak, but we always lean on the ground and lean as best we can in cruise. The spark plugs look great. No excessive lead or carbon fouling. The engine runs great and has an engine monitor. No significant variance in EGTs or CHTs between cylinders. My main concern was with the deposits on #1 & 4 and the dark spot in the center of #3. I plan to fly it for another 25 hours and borescope it again on the next oil change. Thanks for the inputs.