cracked head??

[69heavychevy]

My truck started puffing out white smoke so i parked it for a few days then pulled the heads. When i pulled the valve covers my rocker arms and some of the pushrods were rusted out. Like they had been left in water for days. Is that even possible?? Just kind if caught me off guard. Also i figured cracked heads since the head gasket looks ok. Did have some water in the cylinders but only in #8, #7.