MG MGB
The MGB is a two-door sports car which was manufactured from 1962 until 1980 by the British Motor Corporation and marketed under the MG marque. It was announced and its details first published on 19 September 1962. Introduced as a four-cylinder soft-top roadster, later variants include the MGB GT three-door 2+2 coupé, the six-cylinder sports car and coupé MGC, and the eight-cylinder 2+2 coupé, the MGB GT V8.
Replacing the MGA in 1962, production of the MGB and its variants continued until 1980, though fixed roof GT models ceased export to the US in 1974. Sales for the MGB, MGC and MGB GT V8 combined totaled 523,836 cars. After a 12-year hiatus, the MGB re-entered production as the heavily modified MG RV8 with a limited run of 2,000 cars before its final replacement in 1995 by the MG F.
History
Development of the MGB started at least as early as 1958 with the prototype known by its Abingdon codename; MG EX205. In structure the car was a progressive, modern design in 1962, using a unitary 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. However, components such as brakes and suspension were developments of the earlier 1955 MGA, with the B-Series engine having its origins in 1947. 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 achieved a 0– time of just over 11 seconds. The three-bearing 1,798 cc B-Series engine produced 95 hp at 5,400 rpm – upgraded in October 1964 to a five-bearing crankshaft. From 1975, US-market MGB engines were de-tuned to meet emission standards, ride height was increased by an inch, and distinctive rubber bumpers were fitted to meet bumper standards.
The MGB was one of the first cars to feature controlled crumple zones designed to protect the driver and passenger in a impact with an immovable barrier. Nevertheless, the British AA motoring association has described the car, like many other classic models, as much less safe than modern cars. The issue received public attention following a 2013 case in which a driver in a hired 1963 MGB was killed in a collision with a taxi.
A limited production of 2,000 units of the RV8 was produced by Rover in the 1990s. Despite the similarity in appearance to the roadster, the RV8 had less than 5% parts interchangeability with the original car.
The MGB remains a popular choice for collectors due to inexpensive and readily available parts and simple mechanics.
Drivetrain
All MGBs used the BMC B-Series engine. This engine was essentially an enlarged version of that used in the MGA with engine displacement being increased from 1,622 to 1,798 cc. The earlier cars used a three-main-bearing crankshaft, 18G-series. In February 1964 positive crank-case breathing was introduced and the engine prefix changed to 18GA, until October 1964, when a five-bearing crankshaft design was introduced, the engine prefix became 18GB. Horsepower was rated at 95 net bhp on both five-main-bearing and earlier three-bearing cars with peak power coming at 5,400 rpm with a 6,000 rpm redline. Torque output on the MGB had a peak of and fuel consumption was around. 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 at 5,500 rpm, with torque at 2,500 rpm. Engine prefixes became 18V and the SU carburettor needles were changed for reasons of the latest emission regulations, under ECE15. By 1973 it was ; by 1974 it was 87, with torque; by 1975 it was 85 with. Some California specification cars produced only around by the late 1970s. The compression ratio was also reduced from 9:1 to 8:1 on US spec cars in 1972.All MGBs from 1963 to 1974 used twin SU carburettors. US spec cars from 1975 used a single Stromberg carburettor mounted on a combination intake–exhaust manifold. This greatly reduced power as well as created longevity problems as the catalytic converter tended to crack the intake–exhaust manifold. All MGBs used an SU-built electric fuel pump.
All MGBs from 1962 to 1967 used a four-speed manual gearbox with a non-synchromesh, spur cut first gear. Optional overdrive was available. 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 full synchromesh unit based on the MGC gearbox. This unit was designed to handle the 150net bhp of the three-litre engine of the MGC and was thus over-engineered when mated with the standard MGB B-Series engine. The same transmission was used in the 3.5-litre V8 version of the MGB-GT-V8. An automatic three-speed transmission was also offered as a factory option, but was 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. The overdrive unit was engaged by a toggle switch on the dashboard or by pulling the wiper lever towards the driver, model dependent. The switch was moved to the top of the gearshift knob in 1977. Overdrives were fitted to less than 20% of all MGBs.
There were three different types of overdrive transmissions fitted to the MGB.
1962–1964, 1965–1967
- Laycock Type D OD
- A hole in the bell housing where the starter nose poked through
- "Shield" shaped access cover
- 1020 TPM for OD and 1040 TPM for non-OD
1968 to 1974.5
- Laycock Type LH OD
- Rectangular shaped access cover
- Oval clutch fork boot
- Dipstick
- Black label on the OD solenoid cover stamped "22/61972"
- 1280 TPM for OD and non-OD
- Speedometer drive gear was blue
- Speedometer driven gear was white with 21 teeth
- Laycock Type LH OD
- Rectangular shaped access cover
- Square clutch fork boot
- Side fill plug
- Blue label on the OD solenoid cover stamped "22/6/2005"
- 1000 TPM for OD and non-OD
- Speedometer drive gear was red
- Speedometer driven gear was red with 20 teeth
Early MGBs used the "banjo" type differential carried over from the MGA with the rear axle ratio reduced from the MGA's 4.1 to 3.9 to 1.. 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.
All MGBs were fitted with solid disc brakes on the front with drum brakes on the rear. The front brake calipers were manufactured by Lockheed 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 were installed on all MGBs to comply with US regulations. Servo assistance 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.
The MGB initially had an extremely simple electrical system. Dash-mounted toggle switches controlled the lights, ventilation fan, and wipers with only the direction indicators being mounted on a stalk on the steering column. The ignition switch was also mounted on the dash. Like the MGA, the MGB used 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 difficult; the location gave excellent weight distribution and thus improved handling. The charging system used a Lucas dynamo. Later MGBs had considerable changes to the electrical system including the use of a single 12-volt battery, a change from positive to negative earth, safety-type toggle switches, alternator in lieu of dynamo, additional warning lights and buzzers, and most common functions moved to steering column stalks.
From 1972 there were two different Pirelli Cinturato radial tyre sizes factory-fitted to new cars, depending on whether the car was a roadster, or a GT. With the 1974.5 arrival of the rubber bumper cars the factory-fitted tyre size was simplified to 165/80x14 for all cars, irrespective of whether the car was a roadster or a GT, and also irrespective of the wheel type. The factory built V8s were fitted with alloy wheels and full profile 175HR14 tyres. The "Jubilee" model, made to celebrate the 50th anniversary of the company in 1975, had the alloy wheels from the V8, allegedly because the V8 was not selling and they had a large stock. With a pre-war British racing green colour, tinted glass, gold body stipes and other gold trim, 751 Jubilees were made. One was destroyed in an advertising stunt that went wrong. There are thought to be about half of them left as of 2021. The final 1,000 LE models were the last cars to leave the factory with alloy wheels.
MGB Roadster
The roadster was the first of the MGB range to be produced. The body was a pure two-seater; a small rear seat was a rare option at one point. The MGB offered better space utilisation to passengers and luggage than the preceding MG A, despite being both shorter in wheelbase and overall length, and lower. Growing in width by the same, gave the MGB a distinctly lower and more squat stance than its forebear. The suspension was 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 overdrive transmission. Wheel diameter dropped from 15 to.In late 1967, enough changes were introduced for MG to declare the 1968 model year a Mark II model. Changes included new gearboxes with revised ratios and synchromesh on all four gears, an optional Borg-Warner 35 automatic gearbox, a new rear axle, and an alternator in place of the dynamo with a change to a negative earth system. The Mk II's new gearboxes required significantly altered floorpan sheet metal with a new, flat-topped transmission tunnel.
To meet US safety regulations for the 1968 model year, the MGB received a plastic and foam rubber covered "safety" dashboard, dubbed the "Abingdon pillow", and dual circuit brakes. 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 standardised.
1969 also saw three windscreen wipers instead of two to sweep the required percentage of the glass, high seat backs with head restraints and side marker lamps. The next year saw a new front grille, recessed, in black aluminium. The more traditional-looking polished grille returned in 1973 with a black "honeycomb" insert. In North America, 1970 saw split rear bumpers with the number-plate in between, 1971-1974 returned to the earlier single-piece full-length style chrome bumper.
Further changes in 1972 were to the interior with a new fascia.
To meet impact regulations, 1974 US models had the chrome bumper over-riders replaced with oversized rubber ones, nicknamed "Sabrinas" after the British actress Sabrina. 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 too low. Rather than redesign the front of the car, British Leyland raised the car's suspension by. 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 as a cost-saving measure. The damage done by the British Leyland response to US legislation was partially alleviated by 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.
In March 1979 British Leyland started the production of black painted limited edition MGB roadsters for the US market, meant for a total of 500 examples. Due to a high demand for the limited edition model, production ended with 6,682 examples. The UK received bronze-painted roadsters and a silver GT model limited edition. The production run of homemarket limited edition MGBs was split between 421 roadsters and 579 GTs.
The last MGB roadster produced at Abingdon returned to Abingdon County Hall Museum on 1 December 2011, with the help of British Motor Heritage. It was lifted up 30 feet through a first floor window of the Grade I listed building with inches to spare and now forms part of the collection on display in the main gallery.
Work on a successor for the MGB had been undertaken as early as 1964 with the EX234, but due to the excellent sales of the MGB and MG Midget, BMC cancelled it in 1966. In 1968 a second proposed replacement was developed, the ADO76, but British Leyland had ceased work on that project by the end of 1970; the ADO76 would ultimately become the rubber-bumper version of the MGB in 1974. A third MGB replacement was developed in 1969, this time with a mid-mounted BMC E-series engine, semi-independent Hydrolastic suspension and Ferrari-like styling. This was cancelled in 1970 in favour of the more-conventional Triumph Bullet, which later became the TR7. When the Abingdon factory finally closed in late 1980, British Leyland did not replace it, with the EX234 prototype finally being sold at auction in 2016.
The decision to discontinue the MGB came about largely due to the poor sales performance of the Triumph TR7, which had largely taken over as BL's contemporary offering in the small sports car market. BL management felt that continued production of the MGB was cannibalising the TR7's sales and this therefore was a justification for taking it off the market. However, the TR7 failed to sell and was axed a year later. The MG marque was subsequently used to badge engineer sports versions of the Austin Metro, Austin Maestro and Austin Montego throughout the 1980s, prior to the re-emergence of the MGB in late 1992 as the MG RV8.