Does the block petcock on the engine drain out all of the coolant? Most? Some?

I'd like to drain all the tap water out of the engine before putting everything back together and filling with fresh coolant. Metro Atlanta tap water is fairly soft and has very little mineral content so water heaters last a long time and cooling systems don't corrode like they do with hard water but I'd still like to get as much out as possible.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)