late 1973, facing shrinking Kei-car sales, Mitsubishi narrowed the Minica F4 range down to four equipment levels (Hi-Standard, Deluxe, GL and SL), with the cheaper versions featuring a new grille. The sporty versions were discontinued, as the twin-carb engine fell foul of new emissions regulations. The modified Vulcan S engine came equipped with a balance shaft (later baptised "Silent Shaft") and was cleaner yet, hence the "MCA-II" tag. Power, however, was down to 30 PS. Top speed was . In December 1974, the lineup was again revamped, with the GL and SL becoming the Super Deluxe and Custom. Mitsubishi also lightly redesigned the Minica to accept the new, bigger license plates now required for Kei cars. On 12 April 1976 (March for the Minica 5 Van), corresponding to revised kei car regulations of January 1976 (length up to 3.2 m, width to 1.4 m and engine size to 550 cc) both the sedan and the van received a new long-stroke 471 cc engine, a small increase in length (entirely due to new, larger bumpers), and a new name, the Minica 5. The Minica 5 was the first kei passenger car to meet the new regulations. Both models were also lightly facelifted, featuring new grilles, while equipment levels remained the same. While power output of the new Vulcan 2G22 did not change for the sedan (A104A), the van (A104V) received a lower powered version thereof. The Minica 5 was a mere interim model, anticipating the more thoroughly revised Minica Ami 55 which was soon to arrive. Fourth generation In June 1977 the car and engine grew once again, creating the Minica Ami 55. While the side body panels remained the same, length increased yet a little more (3175 mm) and the entire car was widened by . The updated 546 cc Vulcan 2G23 engine provided for the A105A. Its sibling, the Minica 55 Van (A105V) was updated in March 1977 and was almost impossible to distinguish from the previous Minica 5 Van, aside from badging and a slightly less plasticky front end. The bigger engine provided some useful additional torque, but the sporting Minicas of the early seventies were now a memory. The traditional (and unusual amongst Kei cars) Panhard layout remained. September 1978 brought another engine upgrade: The new "Vulcan II" G23B featured the lean burn MCA-Jet emissions control system with a hemispherical head, aluminium rocker arms and three valves