im guessing burnt valve? 5 are like this and one of the injectors was rusty looking......keep in mind this the truck that was overheating and hardly running....

 

how ya figure burnt valve?

 

look at the attached pics. one of the intake valves i can turn with my fingers.. lots of orange build up o 5 valves too

 

only orange i see is in coolant passages which is due to old coolant

 

send them out to a machine shop and have the valves and deck checked. also magnafluxed for cracks.

clean the block up good with a razor and wipe clean with brakeclean. get a bottoming tap and tap every headbolt holes and clean all the headbolt holes out GOOD.