The Grand Prix formula changed at the end of 1937 limiting engines to 3-liters (supercharged) or 4.5-liter (unblown) so the 4.5-liter V12 supercharged engines that had been used in the 1936/37 Tipo C Alfa Romeos became redundant. At least two were converted to marine use in racing speedboats and powered Antonio Passarin to much success in 1938 and 1939. Probably four others were converted to normally aspirated format, which also necessitated new castings for the lower half of the crankcase…
