Replacing the MGA in 1962, production of the MGB and its variants continued until 1980. 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 finally being replaced 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.[4] In structure the car was an innovative, modern design in 1962, utilizing 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.[5] 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 0–60 mph (97 km/h) time of just over 11 seconds. The three-bearing 1,798 cc B-Series engine produced 95 hp (71 kW) 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 (25 mm), 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 30 mph (48 km/h) impact with an immovable barrier (200 ton).[6][7] 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.[8]
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.
Drivetrain
A sectioned MGB showing engine and gearbox configuration
All MGBs (except the V8 version) used the BMC B-Series engine. This engine was essentially an enlarged version of that used in the MGA with 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 110 lb⋅ft (150 N⋅m) and fuel consumption was around 25 mpg.[9] 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 lb⋅ft (142 N⋅m) 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 94 bhp (70 kW); by 1974 it was 87, with 103 lb⋅ft (140 N⋅m) torque; by 1975 it was 85 with 100 lb⋅ft (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 9:1 to 8:1 on US spec cars in 1972.
All MGBs from 1963 to 1974 used twin 1.5-inch (38 mm) SU carburettors. 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 created longevity problems as the (adjacent) 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, straight-cut first gear. Optional overdrive[10] 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 (until 1977, when overdrive was only operational in fourth)[11] 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. The switch was moved to the top of the gearshift knob in 1977.[11] Overdrives were fitted to less than 20% of all MGBs.
There were three different types of overdrive transmissions fitted to the MGB.
1962–64, 1965–67
Laycock Type D OD (note external solenoid)
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
The gearbox input shaft, flywheel and engine backing plate were changed with the advent of the five-main-bearing engine in 1965. Therefore, the transmission for a three-main-bearing engine (1962–1964) differed from its later counterpart.
1968 to 1974.5
Laycock Type LH OD
Rectangular shaped access cover
Oval clutch fork boot
Dipstick (for checking oil)
Black label on the OD solenoid cover stamped "22/61972"
1280 TPM for OD and non-OD
Speedometer drive gear (on the mainshaft) was blue
Speedometer driven gear (on removable drive housing) was white with 21 teeth
1974.5 to 1980
Laycock Type LH OD
Rectangular shaped access cover
Square clutch fork boot
Side fill plug (no dipstick)
Blue label on the OD solenoid cover stamped "22/62005"
1000 TPM for OD and non-OD
Speedometer drive gear (on the mainshaft) was red
Speedometer driven gear (on removable drive housing) was red with 20 teeth
Overdrive operated in fourth gear only in units made from February 1977 onward.[11]
A sectioned MGB showing the rear axle and differential
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.
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 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 (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.[citation needed]
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 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 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 (rocker) 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,(155/80x14) or a GT,(165/80x14).The original tyres for the majority of MG B’s were 165HR14 Pirelli Cinturato.[12] 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 (wire or RoStyle). Later on during the rubber bumper production period, alloy wheels were introduced on several different limited edition models - with the final 1,000 LE models being the last cars to leave the factory with alloy wheels. The factory built V8s were fitted with full profile 175HR14 tyres.
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