Back in my past, we used to put this solar panel and a battery
out in the wilds on pipe lines to prevent corrosion. A few milli-
amps at a couple volts into the pipe would stop the material migration.
 I don't own a water pumper but I've heard about them from some of 
the other members. And the price of heads. 
 What seems to be happening is a galvanic action caused by heat and 
dissimilar metals. I don't think this would be happening if the heads
were not isolated electricly from the block. 
 I propose a ground strap at least, from head to cylinder body, 
neutralizing any electrical imbalance. If nothing else it seems to me
it would cause pitting around elect. connection. 
 This is just a thought guys, maybe some of you electron hounds can
make something of it.     west

 of course if it works, you'll never know!