If the area is a dead end, I'm sure some sort of acid cleaner might be enough ?

Then pour the cement in.

They usually fill either half or the entire block, often running no cooling water at all, or only through the cylinder head.

So not sure how suitable it might be...again it's back to the temporary thing. But filling from the inside should be a lot better than epoxy from the outside if it can be done.

http://www.hardblok.com/

In your case though you'd only be wanting to fill the dodgy area itself, not the entire block really.