i dont think the dirt road had anything to do with it. bogging would be more likely!

not much else to do. a shot engine is a shot engine. if its just valves though.....why not swap heads? is there something else preventing this? maybe im missing it.....

 

Ouch. I live on 4 miles of dirt road that the county only grades a few times a year. Man talk about washboards but i think the body will fall apart around the engine but the motor will still be ticking.

Sorry about the bad news.

 

after seeing this picture i was not to surprised to read that you had a bad valve. i also wonder why you can't just replace the heads? i guess it just depends on whether there was damage done to the cylinders or not.