Got this block and it has black coating like in front side of coolant passage where is water pump sits. Was wondering what would cause this and how to clean. All other passages further in the block are look clean.

 

That really doesn't appear to be an issue. And if the black came off, you'd just have flush your coolant anyway. Don't worry about it.

 

Thanks for the replay, I was just wandering what would cause something like this and the strangest thing is it's only in the front.

 

Yeah, unless the stuff comes off easily at the touch of your finger I wouldnt worry about it.

 

oxidation i think