You get the idea - why do exhaust valves burn when there is a cracked/compromised exhaust manifold or manifold gasket? Does anybody know the real reason? I know it happens, I just need to know how and why!

 

i think it gets warped from thermal shock, thn it creates an area on the seat where hot exhaust gasses can pass by heating the edge right there till it burns, if the valve doesnt make contact with the seat it cant dissapate its heat and burns. dont take this as gospel im just theorizing

 

My thinking is that the leak somehow creates an overscavenging effect in the one cylinder creating a lean-burn condition causing the cylinder to run hotter than the rest and causing the valve to burn. Just a S.W.A.G. on my part (Scientific Wild Ass Guess).

 

Sucking in air