The original Type 51 emerged in 1931. Its engine was a 160 hp (119 kW) twin overhead cam evolution of the supercharged 2.3 L (2262 cc/138 in³) single overhead cam straight-8 found in the Type 35B.
A victory in the 1931 French Grand Prix was a rare case of success for the line. About 40 examples of the Type 51 and 51A were produced. The Type 51 is visually very similar to the Type 35. The obvious external differences of a Type 51 are: the supercharger blow-off outlet is lower the bonnet in the louvered section; one piece cast wheels instead of bolted on rims; twin fuel caps behind the driver and finally the magneto being off-set to the left on the dash. However many Type 35 cars have been fitted with later wheels, so that is not a reliable signal.