Lycoming valve issues

[jtstric3]

Trying to see if anyone might know what cause this valve to fail? It was a brand new valve(yes brand new not used). I have a 0-360 lycoming. Dropping cylinder off to be overhauled Monday but just curious as to what could have cause it. There was no marks on piston to indicate that the valve hit the piston and I have about 75 hours on the engine since overhaul.

 

[John Fenner]

Valve seat is not ground correctly, the seating area is too far out to the outer edge of the valve face, the seating area should be central to the valve face, I will try to find a picture to illustrate it for you, the edge of the valve on the seat, with likely bad contact full circle of seat caused it to overheat and burn the valve.

 

[jtstric3]

Thanks I haven’t seen anything like this before hopefully my other 3 cylinders Dnt do this too

 

[John Fenner]

Here you go.