FWIW ..D&D Fabrications have probably one of the better web-sites re: B.O.P. and subsequent Rover aluminium V-8 engines. Amongst other points they make is that the casting methods used by G.M at that time ( 1960-1963 ) were flawed.
Notwithstanding, in the short time G.M manufactured the two variations on the 215 CID engine, they pumped out over 750,000 units.
Following the Rover involvement, in 1965, or thereabouts, an entirely different method of casting was employed.....not perfect, but superior to G.M's system. In fairness to G.M, however....production numbers and by definition production economies imposed different and limiting demands