Hanno, rather than fill your block back up with shite, flush your block first.
You can use the recently mentioned phosphoric acid or Muriatic acid (mixed with an inhibitor to stop corroding the good bits) Block off your water pumps and fill the engine to the top. If you set up the water pumps so that you can drain it carefully, you can save the acid in a plastic container for future use. You can let it settle and save most of it. Then give the engine a good flush both ways and once you have it all re assembled and sealed up, put a good corrosion inhibitor (+ antifreeze?) in it. Following all safety advice of course!
I agree with all of Bob's suggestions except that he suffers from some sort of schizophrenia as evidenced by his last line.
