What happened to this valve?

[LarJammer]

Exhaust valve removed from a poorly maintained '80s mechanical injection car, electronic ign. The valve appears to have a slight bend in it, the seat is super clean, not pitted like the other exh valve seats. All chambers are a similar colour but this cyl has much fewer deposits, it has been driven in this state for many miles.

I think the valve has been sticking but tge cleanliness of the seat confuses me. Any ideas?

[PeterBurgess]

Valves tend to rotate in many applications and, even with a knackered valve like you show, the 'good' part can maintain the integrity of the valve seat. Many set ups have devices in built to rotate the valves, some are very intricate with bearing races to aid the turning and even old fashioned ones that do not have a system to rotate them tend to do so to some extent because of the 'twist' in the valve spring as it compresses and relaxes when opening then closing.
Valves usually bed in with a series of little 'dinks' that over a period of time join together and form the seat on the valve. These indentations are usually caused by little flakes of carbon trapping twixt valve and seat and 'dinking' the valve and to some extent on modern inserts the seat as well. These are called carbon indentations and to the uninitiated can be alarming when stripping down for inspection after a few hundred miles! I learned this the hard way in 1987 when I did the first leadfree MGB head, after 1000 miles we inspected, saw the dents, panicked and sent the valves back to G&S for inspection, they soon put me right and it is something I remember to this day

Peter

[Pumaracing]

It's simple enough. The valve has possibly kissed a piston at some time and then burned out on the side where it isn't touching the seat and conducting its heat away. It may also have been bent from the get go.

[Penelope Stopit]

PeterBurgess said:

Valves tend to rotate in many applications and, even with a knackered valve like you show, the 'good' part can maintain the integrity of the valve seat. Many set ups have devices in built to rotate the valves, some are very intricate with bearing races to aid the turning and even old fashioned ones that do not have a system to rotate them tend to do so to some extent because of the 'twist' in the valve spring as it compresses and relaxes when opening then closing.
Valves usually bed in with a series of little 'dinks' that over a period of time join together and form the seat on the valve. These indentations are usually caused by little flakes of carbon trapping twixt valve and seat and 'dinking' the valve and to some extent on modern inserts the seat as well. These are called carbon indentations and to the uninitiated can be alarming when stripping down for inspection after a few hundred miles! I learned this the hard way in 1987 when I did the first leadfree MGB head, after 1000 miles we inspected, saw the dents, panicked and sent the valves back to G&S for inspection, they soon put me right and it is something I remember to this day

Peter

That was a good little read

Thank you