Kohler M20 exhaust valve

[bsadler]

Can anyone explain why my exhaust valves have a groove that looks to be factory. They do not look bad but never have seen a valve that did not have smooth angle. 

[dhoadley]

Can you post a photo?

[bsadler]

[Bill725]

Time for a valve job.

[RAC]

That's wear from contact with the seat. Same advice as above. Valve needs resurfacing and seat will need ground.

[RAC]

There should be a spec on the minimum margin thickness of the valve head. You might be cutting it kinda close by the time that cleans up.

[bsadler]

Thanks all! In the process of grinding and reseating. 
 

[MikeES]

Maybe a 30* valve in a 45* seat?