Failing the combustion test, is awfully indicative of head
gaskets. It means of course that combustion gasses are in the coolant
, you have to ask yourself where could that happen?
Pretty much the heads or gaskets, possible but unlikely a cracked sleeve in a block?
These are dry sleeve motors so that so unlikely as to be almost impossible?
I don’t understand what the machine thinks it’s corrosion
around the water ports
Machinist maybe? Which water ports? Ones in the block?