To compete with the German might of Mercedes-Benz and Auto Union, Alfa Romeo let Vittorio Jano design and build his own V12 Grand Prix car. Called the 12C, it was going to be a successor to the largely successful Tipo B P3.
First prepared in 1936, the twelve liter V12 was impressive in specification, but only drove to two victories at Barcelona and the Vanderbilt cup. For the following season it was upgraded to include twin superchargers and the engine's displacement was increased.
Unfortunately the upgraded cars didn't keep pace with the well developed silver arrows and ace driver Tazio Nuvolari disliked the car's handling. So much so, he defected to the German companies.
While the 12C's racing career seemed over, Alfa Romeo tried once more, refining the chassis, sometimes using a remarkable 16 cylinder engine derived from twin Alfetta 158 engines. As in the years previous the cars didn't work, and Alfa later focused on the Alfetta, selling off the four or so V12 cars. 

engine     V12
position    Front Longitudinal
aspiration    Roots-Type Supercharger
valvetrain    DOHC, 2 Valves per Cyl
fuel feed    2 Weber Carburetors
displacement    4495 cc / 274.3 cu in
bore    72 mm / 2.83 in
stroke    92 mm / 3.62 in
power    320.7 kw / 430 bhp @ 5800 rpm
hp per litre    95.66 bhp per litre
bhp/weight    530.86 bhp per tonne
drive wheels    RWD
body / frame    Aluminum Body on Steel Ladder Frame
front brakes    Drums
rear brakes    Drums
steering    Worm & Sector
f suspension    Arms w/Coil Springs, Hydraulic Dampers
r suspension    Swing Axles w/Transverse Semi-Elliptic Leaf Springs, Hydraulic Telescopic Dampers, Friction Dampers
weight    810 kg / 1786 lbs
wheelbase    2800 mm / 110.2 in
front track    1370 mm / 53.9 in
rear track    1430 mm / 56.3 in
length    4240 mm / 166.9 in
height    1130 mm / 44.5 in
top speed    310.6 kph / 193 mph