1978 MG MGB Mk IV
4-cyl. 1798cc/95hp 2x1bbl
With an experienced team and a lot of data.
Rubber bumper MGBs have been vilified by collectors for their looks and performance, but they have their fans and they’re still among the more popular classic sports cars out there. Designed for the 1975 model year, the Mk IV’s introduction was delayed. The molded polyurethane bumpers added 70 pounds weight and stretched the car 5 inches. They were designed to handle a 5 mph crash without deforming.
The 1975 MGB was also raised 1.5 inches to meet American bumper regulations. This led to considerable body roll and oversteer, neither of which you really want in a sports car. Bigger sway bars were fitted in 1976, but hard cornering now meant lifting an inside wheel. The positioning of the rear sway bar also meant the gas tank was reduced from 12 gallons to 11.
Under the hood, things weren’t encouraging, either. Emissions regulations mandated a catalytic converter, which was positioned below the single Stromberg carburetor that had replaced the twin SUs. The old small-valve cylinder head was exhumed and reduced horsepower to 62.5 bhp. The rear axle ratio was lowered to preserve some acceleration but top speed dwindled to 80-something, despite claims to the contrary. Overdrive was made standard in June 1975 and the GT was discontinued for the U.S.
A number of interior changes arrived in 1977, including a new dash and smaller 15-inch steering wheel. The steering ratio was increased from 3 turns lock-to-lock to 3.5 turns to make up for that. The heater received a two-speed fan and the knobs were replaced by more efficient controls. The overdrive switch was moved to the gear shift, like Triumphs and the pedals adjusted to permit heel-and-toe operation. Inertia reel seatbelts finally appeared. The MGB soldiered on through until 1980, with 14,428 sold that year. In fact, the 500,000th MGB was built in Abingdon in January 1980.
The discrepancy between the current values of rubber bumper MGBs and chrome bumper cars is fairly large, and it is common to restore a rubber bumper car to chrome bumper specifications. It is worth noting, however, that some changes to the later cars were actually improvements, at least in terms of comfort.
Available options on rubber bumper cars were hardtop, AM radio, AM/FM radio wood steering wheel and gearshift, electric clock and air-conditioning (dealer installed). Late cars tend to have most options, though wire wheels were not available and will have been retrofitted.
Later colors range from classic to quite outrageous, while most interiors are black, as are all the tops, but tan upholstery was available with some exterior colors.
The final series of 1,000 black Limited Edition roadsters feature wheels similar to the old