I'm putting heads on a 350 and I noticed something strange...there is a hard material inside one of the water ports on the block. I thought it was strange...I rotated the engine (on a stand) and tried to break the material loose, but it is tough stuff...very hard.

Attached is a picture, with the questionable area circled in red. What do we do? Obviously this is here for some reason that I can't fathom. Do we leave it (seems like a sin), or does is my instinct right that it needs to come out of there? I guess we would rotate the engine upside down and carefully employ the dremel?

Thanks for the advice!
Scott