Library: MGB SpecificationOverview
Dimensions & Weight
Wheelbase:
Track - front:
Track - rear:
Overall length:
Overall width:
Overall height:
Ground clearance:
Turning circle:
Curb/Test weight:91in
49.0in
49.25in
153.2in
59.9in
49.4in
4.2in
32ft
1962
1968
1980
2080 lbs / 2400 lbs
2220 lbs / 2590 lbs
2335 lbs / 2505 lbs
Chassis
Unit Construction body, welded steel constuction, front suspension on subframe.
Steering
Cam Gears rack & pinion system.
Turning circle:
Steering ratio:
Turns lock-to-lock:
Castor angle:
Camber angle:
Kingpin angle:
Toe in:
Grade of oil:32ft (to car 410000, 06/1976)
? (from car 410001)
21.4:1 (as above)
?
2.9 (as above)
3.5
7°
1°
8°
0.1875in
SAE 90EP Hypoid
Brakes
Disc front, drum rear.
Disk size front:
Drum size rear:
Method of operation:10.75in
10in
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
(approximate)
Wheels
Either steel disc bolt-on, or Rudge type wire spoked. Late cars had alloy wheels as option.
For MkI, MkII-on:
Rim size:
Tyre Size:
Tyre pressure:
Wheel bolts:Wires
4J * 14, 5J * 14, 4.5J * 14
5,60 * 14, 165 * 14
(approx 175/70HR14 or 185/70HR14)
21 psi front, 24 psi rear
(+4 for highway)
4 on 4-1/2"
Engine
4 cylinder in line, pushrod, single cam. High or low compression depending on market.
Bore:
Stroke:
Cubic capacity:
Main bearings:
Oil pressure:
Grade of oil:
Sump Capacity:
Firing Order:
Compression ratio HC:
Compression ratio LC:
Compression HC:
Compression LC:
Valve size in/ex:
Cam timing:
Power output:80.26mm
88.90mm
1798cc
18G, 18GA - 3
18GB on - 5
~70psi at 3000rpm
~50psi idle
SAE 20W50
7.5 pints
1-3-4-2
18G - 8.8:1
18V - 9.0:1
8.0:1
18G - 160psi
18V - 170psi
130psi
18G, 18V 74 on - 39.8mm/34.1mm
18V to 74 - 41.3mm/34.1mm
18G - 16/56 51/21
18V - 20/52 55/17
See performance section in Library.
Ignition Timing
Varies with Engine spec, see above.
Distributor points gap:
Dwell:
Spark plugs:
Spark plug gap:
0.015in
60°
NGK BP6ES or Champion N9YC
0.025in (0.030in or more with Sport coil)
0.035in (after 1975)
Carburetter Type
1963 - 1971:
1972 - 1974:
1975 - 1980:Twin SU HS-4
Twin SU HIF-4
Single Zenith-StrombergJet size, main:
Needle & Springs:SU 0.090in
Zenith: 0.100
Various according to carburettor spec.
Clutch
Borg & Beck Single dry plate.
Material:
Number of springs:Ferodo
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.
18G-18GB
(to Oct67)18GD-18V/780
(Nov67-Nov74)18V/797-18V/847
(Dec74-May76)18V/846-18V/893
(Jun76-)First: 3.6363:1 3.440:1 3.036:1 3.333:1 Second: 2.2143:1 2.167:1 Third: 1.3736:1 1.382:1 Third O/D: 1.101:1 to 18GD, 1.133:1 18GF on Top: 1.00:1 Top O/D: 0.802:1 to 18GD, 0.82:1 18GF on Reverse: 4.7552:1 3.095:1
Grade of oil: SAE 20W50 (same as engine)
Capacity: 4.5 pints, 4.7 pints, 6 pints.
Add ~3 pints when O/D fitted
Propellor Shaft
Open shaft, needle roller u/j at each end with grease zerks.
Final Drive
Live axle, hypoid bevel gears. "Banjo" type to Jun-67, "Salisbury" type onwards. Open differential.
Ratio: Manual: 3.909:1 (all years) Auto: 3.7:1 MGC: Early manual: 3.07 Early auto & o/d:
Late manual:3.307 Late o/d: 3.70 MPH per 1000rpm: Manual top: 17.9 Top O/D: 22.1 Auto: 18.91 Grade of oil: SAE 90EP Hypoid Capacity: 1.5 pints
Cooling System
Pressurised, thermostatic control, pump assisted.
Capacity: 12 pints Cap Rating: 1962-67 7 lbs 1968-75 10 lbs 1976 13 lbs 1977-80 15 lbs
Fuel System
Tank located at rear of car under boot floor. Pump points-type attached to battery bracket on right hand side.
Tank capacity: 12 gallons (?) Pump pressure: 2-4 psi (static) Pump rate: SU HP 31.8 Lph SU AUF 300/305 68.2 Lph
Production Data
For a more complete description of the VIN plate found on the dash and the engine number go to the MGB FAQ.
| Model Year |
1st Month |
Car # | Body # | Engine # | ||
|---|---|---|---|---|---|---|
| RD | GT | RD | GT | |||
| 1963 | 5/62 | 101 | MGB/101 | 18G/ /HL101 | ||
| 1964 | 8/63 | 19586 | MGB/26813 | 18GA/ /HL101 | ||
| 1965 | 10/64 | 48766 | ?? | 18GB/ /HL101 | ||
| 1966 | 10/65 | 71441(?) | 71933 | ?? | GBD/101 | 18GB/ /HL101 |
| 1967 | 11/66 | 108039 | ?? | ?? | ?? | 18GB/ /HL101 |
| 1968 | 10/67 | 138401 | 139472 | MGBU/101 | GBUD/500101 | 18GF/ /HL101 |
| 1969 | 10/68 | 158371 | 158233 | MGB/14588# | ?? | 18GH/ /HL101 |
| 1970 | 10/69 | 187211 | 187841 | MGBU/27359 | GBUD/510630 | 18GH/ /HL22209 18GJ/ /HL101 |
| 1971 | 9/70 | 219021 | 219335 | MGBU/300101 | GBUD/520235 | 18GK/ /HL101 |
| 1972 | 5/71 | 258001 | 258004 | MGBU/400101 | GBUD/620101 | 18V/584Z/L101 18V/585Z/L101(OD) |
| 1973 | 8/72 | 294251 | 296001 | MGBU/500101 | GBUD/720101 | 18V/672Z/L101 18V/673Z/L101(OD) |
| 1974 | 8/73 | 328101 | 328801 | MGBU/600101 | GBUD/820101 | 18V/672Z/L14891# 18V/673ZZ/L14891(OD)# |
| 1975 | 12/74 | 367901 | ?? | GU23T/7707 | ?? | 18V/797AE/L101 18V/798AE/L101(OD) |
| 1976 | 9/75 | 386601 | ?? | GU23T/50101 | ?? | 18V/801AE/L101 18V/802AE/L101(OD) |
| 1977 | 6/76 | 410001 | 410351 | GU23T/760000 | ?? | 18V/883AE/L101 18V/884AE/L101(OD) |
| 1978 | 9/77 | 447001 | ?? | GU23T/860000 | ?? | 18V/890AE/L101 18V/891AE/L101(OD) |
| 1979 | 6/78 | 471001 | ?? | GV23T/960000 | ?? | 18V/883AEL/29033# |
| 1980 | 6/79 | 501001 | ?? | GV23T/984080 | ?? | 18V/883AEL/43540# |
|
# These numbers are approximate. Thanks to Caroline Robinson (University Motors), Moss Motors, and Victoria British If you have any of the missing numbers please contact me! | ||||||
Full Specification
Under Construction - Incomplete
Usual disclaimers apply. It is wholly possible I have made typographical errors in the numbers below. Please double check the figures before doing any work and please let me know if you find any errors so I can correct them.Thanks, Skye
| Engine | |
| ENGINE SPECIFICATION & DATA - 1798 c.c. TYPE 18G & 18GA | |
| Engine - General | |
| Type | 4 cylinder in line O.H.V. pushrod operated 18G or 18GA |
| Bore | 3.16 in. (80.26 mm.) |
| Stroke | 3.5 in. (89 mm.) |
| Cubic Capacity | 1789 c.c. (109.8 cu. in.) |
| Compression Radio : High C | 8.8 to 1 |
| Low C | 8.0 to 1 |
| Compression Pressure : High C | 160 lb./sq. in. (11.25 kg./cm2.) |
| Low C | 130 lb./sq. in. (9.15 kg./cm2.) |
| Torque : High C | 110 lb./ft. (15.2 kg.m.) at 3,000 r.p.m. |
| Low C | 105 lb./ft. (14.5 kg.m.) at 3,000 r.p.m. |
| Engine Idle Speed - Optimum | 500 r.p.m. |
| Firing Order | 1,3,4,2 |
| Location of No.1 Cylinder | Next to radiator. |
| Engine Mountings | 3 - one each side of the engine, one under the gearbox |
| Camshaft and Camshaft Bearing | |
| Camshaft Drive | From crankshaft by double roller chain |
| Camshaft Bearings | Three - white metal replaceable liners |
| Camshaft Journal diameter: | |
| Front | 1.78875 to 1.78925 in. (45.424 to 45.437 mm.) |
| Centre | 1.72875 to 1.72925 in. (43.910 to 43.923 mm.) |
| Rear | 1.62275 to 1.62325 in. (41.218 to 41.230 mm.) |
| Camshaft bearings internal diameter after reaming in position in block: |
|
| Front | 1.79025 to 1.79075 in. (45.472 to 45.485 mm.) |
| Centre | 1.73025 to 1.73075 in. (43.948 to 43.961 mm.) |
| Rear | 1.62425 to 1.62475 in. (41.256 to 41.269 mm.) |
| Diametrical clearance | .001 to .002 in. (.0254 to .0508 mm.) |
| End float | .003 to .007 in. (.076 to .178 mm.) |
| Cam lift | .250 in. (6.35 mm.) |
| Timing Chain | 3/8 in. (9.25 mm.) pitch by 52 pitches |
| End thrust | Taken by locating plate |
| Connecting Rods & Big & Little End Bearings | |
| Type | Angular split big end, split clamp small end |
| Length between centres | 6.5 in. (165.1 mm.) |
| Big end bearings - Type | Shell |
| Big end bearings - Material | Steel backed copper-lead |
| Big end bearings - Length | .995 to 1.005 in. (25.2 to 25.52 mm.) |
| Big end bearings - Clearance | .001 to .0027 in. (.0254 to .068 mm.) |
| Endfloat on crankpin | .008 to .012 in. (.20 to .30 mm.) |
| Undersizes available | -.010, -.020, -.030 and -.040 in. (-.254, -.508, -.762, -1.016 mm.) |
| Crankshaft & Main Bearings | |
| Main journal diameter | 2.1265 to 2.127 in. (54.01 to 54.02 mm.) |
| Crankpin journal diameter | 1.8759 to 1.8764 in. (47.648 to 47.661 mm.) |
| Crankshaft end thrust | Taken by thrust washers at centre main bearing |
| Endfloat | .002 to .003 in. (.051 to .076 mm.) |
| Main bearings | Three shell type |
| Bearing material | Steel backed copper-lead |
| Bearing length | 1 1/8 in. (28.5 mm.) |
| Diametrical clearance | .001 to .0027 in. (.0254 to .068 mm.) |
| Undersizes available | -.010, -.020, -.030 and -.040 in. (-.254, -.508, -.762, -1.016 mm.) |
| Cylinder Block | |
| Type | Cylinder cast integral with top half of crankcase |
| Water jackets | Full length |
| Oversize bores : First | .010 in. (.254 mm.) |
| Max. | .040 in. (1.016 mm.) (** .060 and .090 now available) |
| Cylinder Head | |
| Type | Cast iron with vertical valves |
| Port arrangements | Inlet & exhaust ports on same side |
| No. of ports : Exhaust | 2 separate and one siamesed |
| No. or ports : Inlet | 2 siamesed |
| Combustion chamber capacity | 42.5 to 43.5 c.c. (2.59 to 2.65 cu. in.) with valves fitted |
| Gudgeon Pin | |
| Type | Semi-floating. Held by clamp bolt |
| Fit in piston | Free push fit at 20°C (68°F) |
| Outer diameter | .7499 to .7501 in. (19.04 to 19.05 mm.) |
| Lubrication System | |
| Type | Pressure and splash. Wet sump |
| Oil filter | Full flow. Tecalemit felt element. |
| Capacity Oil Filter | 1 pint. (1.2 U.S. pints, .57 litre) |
| Sump capacity | 7 1/2 pints (.42 litre, 9 U.S. pints) |
| Oil cooler capacity | 3/4 pint (.42 litre, .9 U.S. pints) |
| Oil pump - Type | Hobourn-Eaton or eccentric rotor. |
| Pump capacity | 3 1/4 gallons a minute @ 2,000 r.p.m. |
| By-pass valve opens | 12 to 17 lb./sq. in. (4.9 kg./cm2.) |
| Oil pressure relief valve opens | 70 lb./sq. in. (4.9 kg./cm2.) |
| Oil pressure relief valve spring - free length |
3 in. (76.2 mm.) |
| Oil pressure relief valve spring - fitted length |
2 5/32 in. (54.7 mm.) |
| Relief valve spring - load at fitted length |
15.5 to 16.5 lb. (7.0 to 7.5 kg) |
| Normal oil pressure - Idling | Not less than 15 lb./sq. in. (1.05 kg./cm2.) |
| Normal oil pressure - 3,000 r.p.m. | Not less than 50 lb./sq. in. |
| Pistons | |
| Type | Aluminium - Solid skirt |
| No. of rings | 4. 3 compression, 1 oil control |
| Clearance in cylinder : Top | .0036 to .0045 in. (.091 to .121 mm.) |
| Clearance in cylinder : Bottom | .0018 to .0024 in. (.045 to .060 mm.) |
| Width of ring grooves : Top Second Third Oil control |
.064 to .065 in. (1.625 to 1.651 mm.) " " .1578 to .1588 in. (4.008 to 4.033 mm.) |
| Gudgeon pin bore | .7501 to .7503 in. (19.052 to 19.057 mm.) |
| Piston oversizes available | +.010 in., +.020 in., +.030 in., +.040 in. (+.254 mm., +.508 mm., +.762 mm., +1.02mm.) |
| Piston Rings | |
| Top compression ring | Parallel - Cast iron - molybdenum filled |
| 2nd. and 3rd. compression rings | Tapered - Cast iron - molybdenum filled |
| Top ring width | .0615 to .0625 in. (1.562 to 1.587 mm.) |
| 2nd. and 3rd. ring width | .0615 to .0625 in. (1.562 to 1.587 mm.) |
| Top ring fitted gap | .012 to .017 in. (.304 to .431 mm.) |
| 2nd. and 3rd. rings fitted gap | .012 to .017 in. (.304 to .431 mm.) |
| Groove clearance | .0015 to .0035 in. (.038 to .088 mm.) |
| Oil control ring | Slotted scraper |
| Oil control ring - Width | .1552 to .1562 in. (3.94 to 3.96 mm.) |
| Oil control ring fitted gap | .012 to .017 in. (.304 to .431 mm.) |
| Groove clearance | .0016 to .0036 in. (.04 to .09 mm.) |
| Tappets | |
| Type | Barrel with flat base |
| Outside diameter | 13/16 in. (20.64 mm.) |
| Length | 2.293 in. to 2.303 in. (58.25 to 58.5 mm.) |
| Rocker Gear | |
| Length of Rocker Shaft | 14 1/32 in. (356 mm.) |
| Diameter | .624 to .625 in. (15.85 to 15.87 mm.) |
| Rocker arm bore | .7485 to .7495 in. (19.01 to 19.26 mm.) |
| Rocker arm bush - inside diameter | .6255 to .626 in. (15.8 to 15.9 mm.) |
| Ratio | 1.4 to 1 |
| Valves | |
| Head diameter - Inlet | 1.562 to 1.567 in. (38.67 to 38.80 mm.) |
| Head diameter - Exhaust | 1.343 to 1.348 in. (34.11 to 34.23 mm.) |
| Valve seat angle - Inlet & Exhaust | 45 ½° |
| ....... to do | |
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