These four Ballot cars, which were designed in the utmost secrecy, naturally resembled pre-war Peugeots, but Ernest Henry, who took the time during the war to improve his design before the war, resumed his sketch hemi engine with four valves per cylinder, inclined at 60°, controlled by a dual overhead cam head, to equip a straight-eight engine capable of 2900 RPM and giving 150 hp for a top speed of nearly 200 kmph .