There are no bleeder holes in the deck for the lower water jacket. I've never had a KB block, so I could be steering you wrong. I would suggest calling the manufacturer and asking them about using that block in a "continuous duty" situation versus racing duty. In the olden days people would use 400 inch small block chevys(siamese bores) in race apps without the holes in the heads to let the air escape. Worked fine in a drag car, but melted down in street apps. All it takes is a small hole at the highest spot of the waterjacket on the deck to get water where it needs to be.

I agree with cab about broken parts floating into different cylinders.