My calculations were in serious error. It appears it required 10^25 cc of water to flood the Earth - still an incredible number that would require much of the oxygen boung in minerals to be converted to water.
In addition, to flood the Earth in 40 days and 40 nights, it would take 6 inches per minute of rainfall. 12 inches per hour is considered a deluge. (of course there's the minor problem that each inch of rain increases the Earth's diameter requiring even more to keep up the rate).
It is amusing and instructive to work out the total requirement for water to flood from current sea-level to the peak of Everest. When I did this exercise on the back of an envelope I came up with the requirement being a sphere of water around 1200 miles in diameter.