MGB Specification

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Overview

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Chassis

Unit Construction body, welded steel constuction, front suspension on subframe.

 

Wheelbase: 7ft 7in

Track Front: 4ft 1.00in

Rear: 4ft 1.25in

 

Weight (curb/test):

1962 - 2080 lbs / 2400 lbs

1968 - 2220 lbs / 2590 lbs

1980 - 2335 lbs / 2505 lbs

 

Steering

Cam Gears rack & pinion system.

 

Turning circle: 32ft

Castor angle: 7

Camber angle: 1

Kingpin angle: 8

Toe in: 0.1875in

Grade of oil: SAE 90

 

Brakes

Disc front, drum rear.

 

Disk size front: 10.75in

Drum size rear: 10in

 

Method of operation: Hydraulic, vacuum servo assisted as option to 1973, standard thereafter. Dual system some markets from '67. Cable operated parking brake.

 

Suspension

Armstrong lever shocks at 4 corners, integral upper control arm at the front, linked to leaf spring retaining plate at the rear.

 

Grade of oil: 20wt motorcycle fork oil

 

Wheels

Either steel disc bolt-on, or Rudge type wire spoked. Late cars had alloy wheels as option.

 

For MkI, MkII-on: Wires

 

Rim size: 4J * 14, 5J * 14, 4.5J * 14

Tyre Size: 5,60 * 14, 165 * 14

Tyre pressure: 21 psi front, 24 psi rear

 

 

Engine

4 cylinder in line, pushrod ohv.

 

Bore: 80.26mm

Stroke: 88.90mm

Cubic capacity: 1789cc

Oil pressure: ~70psi at speed, ~50psi idle

Grade of oil: SAE 20/50

Sump Capacity: 7.5 pints

Firing Order: 1-3-4-2

 

Compression: Low compression, 135-140psi

High compression, 155-160psi

(compression values should not vary more than 10% across cylinders)

 

Power output: Approx 94bho @ 5500rpm. Later cars had power outputs which varied from market to market (see below). The other tuning details of the unit would be confusing in a table of this type. Please refer to the appropriate Workshop Manual.

 

Ignition Timing

Varies with Engine spec., see above.

 

Distributor points gap: 0.015in

Spark plugs: N9YC

Dwell: 60

Spark plug gap: 0.025in (0.030in or more with Sport coil)

0.035in (after 1975)

 

Carburetter Type

1963 - 1971: Twin SU HS-4

1972 - 1974: Twin SU HIF-4

1975 - 1980: Single Zenith-Stromberg

 

Jet size, main:

Needle recommendation: SU 0.090in, Zenith: 0.100

Various according to carburettor spec.

 

 

Clutch

Borg & Beck Single dry plate

 

Material: Ferodo

Number of springs: Single Diaphragm

 

 

 

Gearbox

Four speed manual, synchromesh on top three ratios to 1965, all synchro after.

Electrical overdrive optional, standard from 1975. Borg Warner 35 automatic gearbox was also available 1967 to 1973.

 

Engine Prefix: 18G- 18GA 18GB on

Ratios: 3sp sync, 4sp sync, B-W auto

Overdrive (where fitted): 0.802, 0.820

Top: 1.000, 1.000, 1.00-1.33

Third O/D (where fitted): 1.10, 1.133

Third: 1.374, 1.382

Second: 2.214, 2.2167, 1.45-1.93

First: 3.640, 3.333, 2.39-3.18

Reverse: 4.760, 3.095, 2.09-2.78

Grade of oil: SAE 30, SAE 20/50 TQF

Capacity: 4.5 pints, 4.7 pints, 6 pints.

 

Add approx. 3pints when O/D fitted

 

Propellor Shaft

Open shaft, needle roller u/j at each end.

 

Final Drive

Live axle, hypoid bevel gears.

 

Ratio: Manual: 3.909:1

Auto: 3.7:1

 

MPH@1000rpm: Manual top: 17.9

O/D: 22.1

Auto: 18.91

 

Grade of oil: SAE 90EP

Capacity: 1.5 pints

 

Cooling System

Pressurised, thermostatic control, pump assisted.

Capacity: 12 pints.

Cap Spec: 7lb for 62-67, 10lb for 68-75, 13lb for 76, and 15lb for 77-80.

 

 

Fuel Tank Capacity

Approx. 12 gallons. Tank located at rear of car under boot floor.

 

 

 

 

 

 

Dimensions & Weight

Wheelbase: 7ft 7in

Track - front: 4ft 1in

Track - rear: 4ft 1.25in

Overall length: 12ft 9.2in

Overall width: 4ft 11.9in

Overall height: 4ft 1.4in

Ground clearance: 4.5in

Turning circle: 32ft

Curb weight: MkII - 2220 lbs

Test weight: MkII - 2590 lbs

 

 

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