Background to the MGB GTV8
The V8 – the MG with effortless performance
Launched in August 1973, the V8 powered MGB combined the popular fixed head coupe body style with a powerful three and half litre light alloy V8 engine. The Rover powerplant ran with a reduced compression ratio but an increased torque compared with the similar engines then used in the Rover saloons. The result transformed the MGB, creating a very nimble car with the luxury of multi-cylinder power which is both flexible and economical – features which continue to have a special appeal for V8 enthusiasts today!
On the road the MGBGTV8 has an effortless performance, accelerating rapidly in the higher gears with 125 mph available in both direct and overdrive top. Hills just melt away and the torque gives the car an unfussy manner. The 0 to 60 time of 7.7 seconds is still 30 years later, a time many of today’s sports saloons cannot touch. Even when asked to work hard, the exhaust note retains its very pleasingly modest but purposeful burble in keeping with its understated manner.
The V8 engine, although from an old Buick design from the early fifties, contains hydraulic cam followers which give the MGBGTV8 a quietness that compliments the smooth power. Under the bonnet, the lightweight aluminium V8 engine seems much bigger than the original four cylinder steel engine but is only just a little heavier when the engine ancillaries are included. The lightweight benefits are good front to rear weight distribution and an appreciable increase in the power to weight ratio, even from the detuned 137 bhp V8 power unit.
A surprising feature of the MGBGTV8 is the fuel economy. Even driven on the open road with a sense of fun the enthusiast can enjoy with V8 power, it is quite easy to achieve between 27 and 31 miles to the gallon. The overdrive unit gives the MGBGTV8 long legs with around 29 mph per 1,000 rpm or 3,000 rpm at 90 mph. The convenient overdrive facility is available on top gear at the flick of a stalk switch on the steering column and on many of the earlier chrome bumpered examples of the model, it is available on third gear as well.
The MGBGTV8 is however not without its poor features – excessive wind noise at speed and a choppy ride at slow speeds from the stiffer rear springs which are needed to cope with the higher power output. The gearbox has to be treated with consideration when punching the additional power through to the road wheels.
At its launch in 1973, the MGBGTV8 was welcomed as a powerful example of the MG marque but generally regarded as arriving several years late in a popular but ageing bodyshell and suspension package, then over ten years old. The MGBGTV8 is very much an MG combining the famous marque’s Safety Fast! features – speed and performance with predictable and forgiving handling characteristics. At the time of the launch, the specification of servo assisted brakes, tinted glass, distinctive light alloy wheels, fine cord covered adjustable seats, two speed wipers and an overdrive as standard made it a refined sports car for 1973 and good value at its launch price of £2,294. In so many ways the MGBGTV8 is an undiscovered classic sportscar and prices have never been driven up by “chequebook investors”.
V8 technical specification and data
Engine type Rover 3.5 litre V8
Location & drive In-line front with rear wheel drive
Number of cylinders 8
Layout 90 degree Vee in two banks
Bore 3.50 in (88.90 mm)
Stroke 2.80 in (71.12 mm)
Compression ratio 8.26 : 1
Firing order 1, 8, 4, 3, 6, 5, 7 , 2
..left bank 1, 3, 5, 7
..right bank 2, 4, 6, 8
Idle speed 800 to 850 rpm
Fast idle speed 1,400 to 1,500 rpm
Oil pressure – normal 30 to 40 lb/sq in (2.0 to 2.8 kg/sq cm)
Cylinder head Aluminium alloy
Cylinder block Aluminium alloy
Valve gear Single cam with two valves per cylinder
Maximum power output 137 bhp at 5,000 rpm
Maximum torque 193 lb.ft at 2,900 rpm
Ignition Lucas distributor
Timing at 1,000 rpm 8 degrees BTDC
Timing marks On the crankshaft pulley pointer attached to the front of the cylinder block
Dwell angle 28 degrees
Contact breaker gap 0.014 to 0.016 in (0.35 to 0.40 mm)
Spark plug type Champion L-92Y now NGK 4111 BP5HS
Spark plug gap 0.035 in (0.90 mm)
Fuel system Twin SU HIF6 carburettors
Recommended octane rating 94 RON minimum
Carburettor needle BBU
Carburettor spring colour Yellow
Fuel pump SU type AUF305 electric
Circuit polarity Negative earth
Voltage 12 volt
Batteries Twin 6 volt, later one 12 volt
Capacity (20 hour rated) 67 amp hour
Fuses 35 amp (blow rating)
Gearbox, manual Four speed, all synchromesh gearbox with reverse. Laycock overdrive on third
and fourth gears on the early cars and on fourth only on cars from around Car No. GD2D1 1400
First 3.138 : 1
Second 1.974 : 1
Third 1.259 : 1
Fourth 1 : 1
Overdrive 0.82 : 1
Fourth gear speed per 1,000 rpm 23.0 mph (37 kph)
Overdrive top speed per 1,000 rpm 28.5 mph (45 kph)
Rack and pinion with collapsible steering column. Turning circle 34 ft (10.36 m) left lock and 33 ft 1 in (10.1 m) right lock.
Independent with coil springs and lower wishbone mounted on a crossmember assembly. Lever arm shock absorbers with double levers carrying the top end of the swivel pin. Anti-roll bar.
Tube type live axle with three quarter floating drive shafts. Semi- elliptic multi-leaf springs. Lever type shock absorbers.
Front: 10.7 in (272 mm) diameter solid discs. Rear: 20 in (254 mm) diameter drums. Servo assisted hydraulic.
Wheels and tyres
Wheel size 5J x 14
Wheel nut tightness 60 lbf.ft (8 kgf.m, 81 Nm)
Tyres size 175HR x 14
Tyre type Radial ply
Overall length Chrome: 154.75 in (3,931 mm)
Rubber: 158.25 in (4,020 mm)
Overall width 59.94 in (152.3 cm)
Overall height 49.97 in (126.9 cm)
Ground clearance 4.25 in (108.0 mm) minimum
Track front 49.0 in (124.4 cm)
Track rear 49.25 in (125 cm)
Wheel base 91.125 in (231.5 cm)
Fuel tank 12 gallons (54 litres)
Engine and oil cooler, refill with filter change. Filter 0.5 pint
(0.28 litres) 8 pints (4.54 litres)
Gearbox and overdrive 6 pints (3.4 litres)
Rear axle 1.5 pints (0.85 litres)
Cooling system with heater 16 pints (9.08 litres)
Windscreen washer bottle 3 pints (1.71 litres)