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MG MGB

MG MGB

The MGB is a sports car launched by MG Cars in May 1962 to replace the MGA. Introduced as a four-cylinder roadster, a coupé with 2+2 seating was added in 1965. The six-cylinder MGC debuted in 1967; a later derivative fitted with the Buick-based Rover V8 was made from 1973 to 1976.

MGB/MGC production continued until October 1980 variously by the British Motor Corporation and its successors, British Motor Holdings and British Leyland Motor Corporation.

History

The MGB was a relatively modern design at the time of its introduction, utilizing a monocoque structure instead of the traditional body-on-frame construction used on both the MGA and MG T-types and the MGB's rival, the Triumph TR series. The lightweight design reduced manufacturing costs while adding to overall vehicle strength. Wind-up windows were standard, and a comfortable driver's compartment offered plenty of legroom. A parcel shelf was fitted behind the seats.

The MGB's performance was considered brisk at the time of its introduction, with a 0–60 mph (96 km/h) time of just over 11 seconds, aided by the relatively light weight of the car. Handling was one of the MGB's strong points. The 3-bearing 1798 cc B-Series engine produced 95 hp (71 kW) at 5,400 rpm. The engine was upgraded in October 1964 to a five-bearing crankshaft in an effort to improve reliability. A majority of MGBs were exported to United States. In 1974, as US air pollution emission standards became more rigorous, US-market MGBs were de-tuned for compliance. As well as a marked reduction in performance, the MGB gained an inch (25 mm) in ride height and the distinctive rubber bumpers which came to replace the chrome for all markets.

The MGB was one of the first cars to feature controlled crumple zones designed to protect the driver and passenger in a 30 mph (48 km/h) impact with an immovable barrier (200 ton).

Combined production volume of MGB, MGC and MGB GT V8 models was 523,836 cars. A very limited-production "revival" model with only 2,000 units made, called RV8 was produced by Rover in the 1990s. Despite the similarity in appearance to the roadster, the RV8 had less than 5 percent parts interchangeability with the original car.

Drivetrain

Engine: All MGBs (except the V8 version) utilized the BMC B-Series engine. This engine was essentially an enlarged version of that used in the MGA with displacement being increased from 1622 cc to 1798 cc. The earlier cars used a three main bearing crankshaft until mid-1965, when a five-bearing crankshaft design was introduced. Horsepower was rated at 95 on both 3 main bearing and earlier 5-bearing cars with peak power coming at 5400 rpm with a 6000 rpm redline. Torque output on all MGB is good with a peak of 110 ft·lb (150 N·m) Fuel consumption was around 25mpg.. US specification cars saw power fall in 1968 with the introduction of emission standards and the use of air or smog pumps. In 1971 UK spec cars still had 95 bhp (71 kW) at 5,500 rpm, with 105 ft·lb (142 N·m) torque at 2500 rpm. By 1973 it was 94 bhp (70 kW); by 1974 it was 87, with 103 ft·lb (140 N·m) torque; by 1975 it was 85 with 100 ft·lb (140 N·m). Some California specification cars produced only around 70 hp (52 kW) by the late 1970s. The compression ratio was also reduced from 9 to 1 to 8:1 on US spec cars in 1972.

Carburation: All MGBs from 1963 to 1974 used twin 1.5-inch (38 mm) SU carburetors. US spec cars from 1975 used a single Stromberg 1.75-inch (44 mm) carburettor mounted on a combination intake–exhaust manifold. This greatly reduced power as well as creating longevity problems as the (adjacent) catalytic converter tended to crack the intake–exhaust manifold. All MGBs used a SU-built electronic fuel pump.

Gearbox: All MGBs from 1962 to 1967 used a four-speed manual gearbox with a non-synchronized (or straight-cut) first gear with optional overdrive[5].. This gearbox was based on that used in the MGA with some minor upgrades to cope with the additional output of the larger MGB engine. In 1968 the early gearbox was replaced by a fully synchronized unit based on the MGC gearbox. This unit was designed to handle the 150 hp 3-litre engine of the MGC and was thus over-engineered when mated with the standard MGB B-Series engine. In fact, the same transmission was even used in the 3.5-litre V-8 version of the MGB-GT-V8. An automatic three-speed transmission was also offered as a factory option but proved to be fairly unpopular.

Electrically engaged overdrive gearboxes were an available option on all MGBs. The overdrive unit was operational in third and fourth gears but the overall ratio in third gear overdrive was roughly the same as fourth gear direct. Later cars allowed the overdrive to operate only in fourth gear. The overdrive unit was engaged by a toggle switch located on the dash on 1963–1974 cars and on a gear lever mounted switch on later cars. Overdrives were fitted to less than 20% of all MGBs, making it a very desirable feature.


Rear axle: Early MGBs used the "banjo" type differential carried over from the MGA with the rear axle ratio reduced from the MGA's 4.1 (or 4.3) to 3.9 to 1. (Compensating for the reduction from 15 inch to 14-inch (360 mm) wheels.) MGB GTs first began using a tube-type rear axle in 1967. This unit was substantially stronger being, like the later gearbox, designed for the three-litre MGC. All MGBs used the tube-type axle from 1968.

Brakes: All MGBs were fitted with 11-inch (280 mm) solid (non-ventilated) disc brakes on the front with drum brakes on the rear. The front brake calipers were manufactured by Girling and used two pistons per caliper. The brake system on the MGB GT was the same as the Roadster with the exception of slightly larger rear brake cylinders. A single-circuit hydraulic system was used before 1968 when dual-circuit (separate front and rear systems) were installed on all MGBs to comply with US regulations. Servo assistance (power brakes) was not standard until 1975. Many modern and contemporary testers have commented on the very heavy brake pedal pressure needed to stop the non-servo assisted cars.

Electrical system: The MGB initially had an extremely simple electrical system. Dash-mounted toggle switches controlled the lights, ventilation fan, and wipers with only the turn signals being mounted on a stalk on the steering column. The ignition switch was also mounted on the dash. Like the MGA, the MGB utilized two 6-volt batteries wired in series to give a 12-volt positive earth configuration. The batteries were placed under a scuttle panel behind the seats making access a bit of a challenge but the location gave excellent weight distribution and thus improved handling. The charging system used a Lucas generator (dynamo).

Later MGBs had considerable changes to the electrical system including the use of a single twelve-volt battery, a change from positive to negative earth, safety-type toggle switches, an alternator in place of the generator, additional warning lights and buzzers, and having most common functions moved to steering column stalks.

MGB Roadster

The roadster was the first of the MGB range to be produced. The body was a pure two-seater but a small rear seat was a rare option at one point. By making better use of space the MGB was able to offer more passenger and luggage accommodation than the earlier MGA while being 3 inches (75 mm) shorter overall. The suspension was also softer, giving a smoother ride, and the larger engine gave a slightly higher top speed. The four-speed gearbox was an uprated version of the one used in the MGA with an optional (electrically activated) overdrive transmission. Wheel diameter dropped from 15 to 14 inches (360 mm).

Mark II

In late 1967, sufficient changes were introduced for the factory to define a Mark II model. Changes included synchromesh on all 4 gears with revised ratios, an optional Borg-Warner automatic gearbox (except in the US), a new rear axle and an alternator in place of the dynamo with a change to a negative earth system. To accommodate the new gearboxes there were significant changes to the sheet metal in the floorpan, and a new flat-topped transmission tunnel. All models are rear-wheel drive. To meet US safety regulations, later North American tourers got three windscreen wipers instead of just two (to sweep the required percentage of the glass), and also received a plastic and foam rubber covered "safety" dashboard, dubbed the "Abingdon pillow". Other markets continued with the steel dashboard. Rubery Owen ROstyle wheels were introduced to replace the previous pressed steel versions in 1969 and reclining seats were standardized in 1970. 1971 also saw a new front grille, recessed, in black aluminium. The more traditional-looking polished grille returned in 1972 with a black "honeycomb" insert. 1970 saw split rear bumpers with the number-plate in between, 1971 returned to the earlier five-piece style.

Mark III

Further changes in 1972 brought about the Mark III. The main changes were to the interior with a new fascia and improved heater.

Early in the 1974 model year, to meet impact regulations, US models saw the chrome bumper over-riders replaced with large rubber ones, nicknamed "Sabrinas" after the well-endowed British actress.

In the second half of 1974 the chrome bumpers were replaced altogether. A new, steel-reinforced black rubber bumper at the front incorporated the grille area as well, giving a major restyling to the B's nose, and a matching rear bumper completed the change.

New US headlight height regulations also meant that the headlamps were now too low. Rather than redesign the front of the car, British Leyland raised the car's suspension by 1-inch (25 mm). This, in combination with the new, far heavier bumpers resulted in significantly poorer handling. For the 1975 model year only, the front anti-roll bar was deleted from the standard car as a cost-saving measure (though it was still available as an option). The damage done by the British Leyland response to US legislation was partially alleviated by further revisions to the suspension geometry in 1977, when a rear anti-roll bar was made standard equipment on all models.

US emissions regulations also reduced horsepower, and by the time of the B's demise in 1980, performance was decidedly lacklustre.

Work on a successor for the MGB had been undertaken as long ago as 1968, but British Leyland had pulled the plug on that project by the end of 1970. When the Abingdon factory finally closed in the autumn of 1980, British Leyland did not replace it. However, Aston Martin had expressed an interest in buying the Abingdon plant and continuing MGB production there; this, too, failed to materialise.

V8 Conversions

After MG began offering and introducing V8 engines for the MGB GT in 1973, custom fittings started being offeed by mechanics to allow V8 conversions in the Roadster. While these remained unofficial, conversions became extremely popular throughout the 70s and the early 80s.

MGB GT

The fixed-roof MGB GT was introduced in October 1965. Production continued until 1980, though export to the US ceased in 1974. The MGB GT sported a ground-breaking greenhouse designed by Pininfarina and launching the sporty "hatchback" style. By combining the sloping rear window with the rear deck lid, the B GT offered the utility of a station wagon while retaining the style and shape of a coupe. This new configuration was a 2+2 design with a right-angled rear bench seat and far more luggage space than in the roadster. Relatively few components differed, although the MGB GT did receive different suspension springs and anti-roll bars and a different windscreen which was more easily and inexpensively serviceable. Early prototypes such as the MGB Berlinette produced by the Belgian coach builder Jacques Coune utilized a raised windscreen in order to accommodate the fastback.

Acceleration of the GT was slightly slower than that of the roadster due to its increased weight. Top speed improved by 5 mph (8 km/h) to 105 mph (170 km/h) due to better aerodynamics.
MG BGT

MG BGT rear view

MGB GT V8

MG began offering the MGB GT V8 in 1973 utilising the ubiquitous aluminium-block 3528 cc Rover V8 engine, first fitted to the Rover P5B. This engine had been used in the A-body platform Buick Special and Oldsmobile F-85 and was the lightest mass-production V8 in the world, with a dry weight of only 318 lb (144 kg), and was about 60 lb (27 kg) lighter than its 4-cylinder counterpart by the MOWOG (Morris-Wolseley Garages) foundry. Some improvements were made by MG-Rover, and the engine found a long-lived niche in the British motor industry. These cars were similar to those already being produced in significant volume by tuner Ken Costello. MG even contracted Costello to build them a prototype MGB GT V8.

However, the powerful 180 bhp (134 kW) engine used by Costello for his conversions was replaced for production by MG with a more modestly tuned version producing only 137 bhp(102 kW) at 5000 rpm. But 193 lb·ft (262 N·m) of torque helped it hit 60 mph (97 km/h) in around 8 seconds, and go on to a respectable 125 mph (201 km/h) top speed.

By virtue of its aluminium cylinder block and heads, the Rover V8 engine actually weighed approximately forty pounds less than MG's iron four-cylinder. Unlike the MGC, the V8 that provided the MGB GT V8's increased power and torque did not require significant chassis changes nor sacrifice handling.

Only GT versions of the V8-powered MGB were produced by the factory. Production ended in 1976.

MG never attempted to export the MGB GT V8 to the United States. They chose not to develop a left-hand-drive version or to seek US air pollution emission certification of the MGB GT V8, although the Rover V8 engine was offered in US-bound Rover models throughout the same period and beyond. British Leyland Motor Corporation management cited insufficient production capacity to support anticipated demand for the V8 engine in MGB GT, so they priced the MGB GT V8 high.

The MGB GT V8 was very warmly received by the automotive press, but British Leyland Motor Corporation was reportedly concerned that the MGB GT V8 would overshadow their other products, including the more expensive Triumph.

Australian Assembly

The MGB was assembled in Australia from 1963 to 1972, during which time approximately 9,000 were sold. The cars were assembled from complete knock down kits shipped from England. The arrangement ended in 1972 when the government issued a requirement that to enjoy favourable tariff treatment locally produced cars should feature 85% local content. At the time the local content of the Australian assembled MGBs was evaluated as just 45%.

Motorsport

Specially tuned MGBs (including some made out of aluminium) were successful in international road competition events, scoring a Grand Touring category victory in the 1965 Monte Carlo Rally. Circuit racing wins included the Guards 1000 miles race at Brands Hatch in 1965 and the 84-hour Marathon de la Route at the Nurburgring in 1966. MGBs also won the GT Category in the 1966 Targa Florio, the 1966 Spa 1000 and the 1967 Spa 1000.

Gallery

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MG vehicles


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