Mini Cooper 997cc (type 9F)

Engine Data  
Number of Cylinders 4
Bore 2.458in (62.43mm)
Stroke 3.20in (81.28mm)
Capacity 60.87 cu in (997cc)
Compression Ratio (H prefix) 9.1
Compression Ratio (L prefix) 8.3:1
BMEP (H prefix) 134 psi (9.42kg/cm2) at 3500rpm
BMEP (L prefix) 129 psi (9.07kg/cm2) at 3500rpm
Torque (H prefix) 54 lbft (7.46 kgm) at 3600rpm
Torque (L prefix) 53 lbft (7.32 kgm) at 3500rpm
Peak Power (claimed) 55 bhp
   
Crankshaft Data  
Main Bearing Material Steel-backed copper-lead; thin wall
Main Bearing Length 1.0625in (26.99mm)
Main Bearing Running Clearance 0.001 to 0.0027 in (0.025 to 0.069mm)
   
Con Rods  
Big-end Bearing Material Steel-backed copper-lead;thin wall
Big-end Bearing Length 0.875in (22.22mm)
   
Pistons  
Type Solid skirt
Clearance (bottom of skirt - pressure face) 0.0016 to 0.0022in (0.041 to 0.056mm)
   
Piston Rings  
Top Plain, chrome-faced
Second and third Tapered
Width 0.0615 to 0.0625in (1.563 to 1.588mm)
   
Valves and Valve Gear  
Inlet Valve Diameter 1.156in (29.4mm)
Exhaust Valve Diameter 1.000in (25.4mm)
Inlet Throat Diameter 1.0312in (26.2mm)
Exhaust Throat Diameter 0.908in (23.06mm)
Valve Lift 0.312in (7.92mm)
Inlet Valve Opening 16 degrees BTDC
Inlet Valve Closing 56 degress ABDC
Exhaust Valve Opening 51 degrees BBDC
Exhaust Valve Closing 21 degrees ATDC
(Valve timings measured with 0.019in/0.48mm rocker clearance set for testing purposes only).  
Valve Spring Free Length (all valves) 1.750in (44.45mm)
Valve Spring No. of Working Coils 4.5
Valve Spring Pressure - Open (all valves) 90lb (40.7kg)
Valve Spring Pressure - Closed (all valves) 55lb (24.9kg)
   
Camshaft  
Journal Diameter (Front) 1.6655 to 1.666in (42.304 to 42.316mm)
Journal Diameter (Centre) 1.62275 to 1.62325in (41.218 to 41.231mm)
Journal Diameter (Rear) 1.3725 to 1.3735in (34.862 to 34.887mm)
End Float 0.003 to 0.007in (0.076 to 0.178mm)
Bearings 3, steel-backed white metal
Bearing Inside Diameter (reamed in position)  

Front Bearing

1.667 to 1.6675in (42.342 to 42.355mm)
Centre Bearing
1.6245 to 1.6255in (41.261 to 41.287mm)
Rear Bearing
1.3748 to 1.3755in (34.914 to 34.937mm)
   
Engine Lubrication  
Oil Pump Type Hobourn-Eaton
Relief Pressure Valve Operates 70 psi (4.92 kg/cm2)
Relief Valve Spring (Free Length) 2 39/64in (66.28mm)
Relief Valve Spring (Fitted Length) 2 5/32in (54.77mm)
Oil Pressure (Normal Running) 70psi (4.92kg/cm2)
Oil Pressure (Idling - Minimum) 15psi (1.05kg/cm2)
   
Cooling System  
Thermostat temperature 83 degrees Celsius (180 degrees F)
   
Clutch  
Pressure Springs (Colour) Black enamel with white spot
Diaphragm Spring (Colour Code) Light green

 

Mini Cooper 998cc (type 9FA, 9FD)

Engine Data  
Number of Cylinders 4
Bore 2.543in (64.588mm)
Stroke 3.00in (76.2mm)
Capacity 60.96 cu in (998cc)
Compression Ratio (H prefix) 9.1
Compression Ratio (L prefix) 7.8:1
BMEP (H prefix) 142 psi (10kg/cm2) at 3000rpm
BMEP (L prefix) 135 psi (9.5kg/cm2) at 3000rpm
Torque (H prefix) 57 lbft (7.881 kgm) at 3000rpm
Torque (L prefix) 56 lbft (7.74 kgm) at 2900rpm
Peak Power (claimed) 55 bhp
   
Crankshaft Data  
Main Bearing Material Steel-backed copper-lead or aluminium-tin; thin wall
Main Bearing Length 1.0625in (26.99mm)
Main Bearing Running Clearance 0.001 to 0.0027 in (0.025 to 0.069mm)
   
Con Rods  
Big-end Bearing Material Steel-backed copper-lead or aluminium-tin; thin wall
Big-end Bearing Length 0.875in (22.22mm)
   
Pistons  
Type Solid skirt
Clearance (bottom of skirt - pressure face) 0.0005 to 0.0011in (0.013 to 0.028mm)
First Oversize Bore +0.010in (0.254mm)
Second Oversize Bore +0.020in (0.508mm)
   
Piston Rings  
Top Plain, chrome-faced
Second and third Tapered
Width 0.0620 to 0.0625in (1.574 to 1.588mm)
Thickness (all rings) 0.106 to 0.112in (2.692 to 2.835mm)
   
Gudgeon Pin  
Type Fully floating, with circlip location
Fit in Piston 0.001in (0.0025mm) tight to 0.00035in (0.0089mm) slack
Fit in Small End 0.0002in (0.005mm) slack, to size.
Diameter 0.6244 to 0.6247in (15.86 to 15.867mm)
   
Valves and Valve Gear  
Inlet Valve Diameter 1.219in (30.86mm)
Exhaust Valve Diameter 1.00in (25.4mm)
Inlet Throat Diameter 1.172in (29.77mm)
Exhaust Throat Diameter 0.908in (23.06mm)
Valve Lift 0.312in (7.92mm)
Inlet Valve Opening 5 degrees BTDC
Inlet Valve Closing 45 degress ABDC
Exhaust Valve Opening 51 degrees BBDC
Exhaust Valve Closing 21 degrees ATDC
(Valve timings measured with 0.019in/0.48mm rocker clearance set for testing purposes only).  
Outer Valve Spring Free Length (all valves) 1.750in (44.45mm)
Inner Valve Spring Free Length (all valves) 1.672in (42.47mm)
Inner Valve Spring Pressure - Open (all valves) 30lb (13.6kg)
Inner Valve Spring Pressure - Closed (all valves) 18lb (8.17kg)
Outer Valve Spring Pressure - Open (all valves) 88lb (39.9kg)
Outer Valve Spring Pressure - Closed (all valves) 55.5lb (25.13kg)
   
Camshaft  
Journal Diameter (Front) 1.6655 to 1.666in (42.304 to 42.316mm)
Journal Diameter (Centre) 1.62275 to 1.62325in (41.218 to 41.231mm)
Journal Diameter (Rear) 1.3725 to 1.3735in (34.862 to 34.887mm)
End Float 0.003 to 0.007in (0.076 to 0.178mm)
Bearings 3, steel-backed white metal
Bearing Inside Diameter (reamed in position)  

Front Bearing

1.667 to 1.6675in (42.342 to 42.355mm)
Centre Bearing
1.6245 to 1.6255in (41.261 to 41.287mm)
Rear Bearing
1.3748 to 1.3755in (34.914 to 34.937mm)
   
Engine Lubrication  
Oil Pump Type Hobourn-Eaton
Relief Pressure Valve Operates 70 psi (4.92 kg/cm2)
Relief Valve Spring (Free Length) 2 39/64in (66.28mm)
Relief Valve Spring (Fitted Length) 2 5/32in (54.77mm)
Oil Pressure (Normal Running) 70psi (4.92kg/cm2)
Oil Pressure (Idling - Minimum) 15psi (1.05kg/cm2)
   
Cooling System  
Termostat temperature 83 degrees Celsius (180 degrees F)
   
Clutch  
Pressure Springs (Colour) Black enamel with white spot
Diaphragm Spring (Colour Code) Light green

 

Mini Cooper S 970cc, 1071cc, 1275cc (essentially the same engine with varied deck height and stroke)

Engine Data  
Number of Cylinders 4
Bore 2.780in (70.6mm)
Stroke (970cc) 2.4375in (61.91mm)
Stroke (1071cc) 2.687in (68.26mm)
Stroke (1275cc) 3.2in (81.33mm)
Compression Ratio (970cc) 10:1
Compression Ratio (1071cc) 9:1
Compression Ratio (1275cc) 9.75:1
Combustion Chamber Volume (valves and spark plugs fitted) 1.306cu.in. (21.4cc)
BMEP (970cc) 142 psi (10kg/cm2) at 4500rpm
BMEP (1071cc) 143 psi (10.05kg/cm2) at 4500rpm
BMEP (1275cc) 153 psi (10.76kg/cm2) at 3000rpm
Compression Pressure 190 to 200 psi (13.3 to 14.07kg/cm2) at 500rpm
Engine Idle Speed 500rpm approx.
   
Crankshaft Data  
Main Bearing Material Steel-backed copper-lead; thin wall
Main Bearing Length 1.000in (25.4mm)
Main Bearing Running Clearance 0.001 to 0.0027in (0.025 to 0.069mm)
Main Journal Diameter 2.0005 to 2.0010in (50.81 to 50.82mm)
Main Journal Minimum Regrind Diameter 1.9805 to 1.9810in (50.30 to 50.31mm)
   
Con Rods  
Little-end Bore Diameter 0.8110 to 0.8115in (20.60 to 20.61mm)
   
Pistons  
Type Solid skirt
Clearance (bottom of skirt - pressure face) 0.0019 to 0.0025in (0.048 to 0.063mm)
Clearance (top of skirt) 0.025 to 0.283in (0.63 to 0.72mm)
   
Piston Rings  
Top Plain
Second and third Tapered
Width 0.0459 to 0.0469in (1.16 to 1.19mm)
Thickness (all rings) 0.116 to 0.122in (2.94 to 3.09mm)
Fitting Gap (all rings) 0.08 to 0.013in (0.2 to 0.33mm)
Clearance in Groove (all rings) 0.0015 to 0.0035in (0.04 to 0.09mm)
Oil Control Ring Width 0.1553 to 0.1563in (3.94 to 3.96mm)
   
Gudgeon Pin  
Type Pressed-in con rod
Fit in Piston Hand push-fit
Fit in Con Rod 0.0008 to 0.015in (0.020 to 0.038mm) interferences
Diameter 0.8123 to 0.8125in (20.63 to 20.64mm)
   
Valves and Valve Gear  
Inlet Valve Diameter 1.401 to 1.406in (35.58 to 35.71mm)
Exhaust Valve Diameter 1.214 to 1.219in (30.83 to 30.96mm)
Valve Lift 0.318in (8.08mm) nominal
Inlet Valve Opening 5 degrees BTDC
Inlet Valve Closing 45 degress ABDC
Exhaust Valve Opening 51 degrees BBDC
Exhaust Valve Closing 21 degrees ATDC
(Valve timings measured with 0.021in/0.53mm rocker clearance set for testing purposes only).  
Valve Rocker Clearance (Standard) 0.012in (0.39mm) cold
Valve Rocker Clearance (Competition) 0.015in (0.38mm) cold
Valve Rocker Clearance (Timing) 0.021in (0.53mm)
Outer Valve Spring Free Length (all valves) 1.740in (44.19mm)
Inner Valve Spring Free Length (all valves) 1.705in (43.31mm)
Inner Valve Spring Pressure - Open (all valves) 46lb (20.865kg)
Inner Valve Spring Pressure - Closed (all valves) 26.6lb (12.065kg)
Outer Valve Spring Pressure - Open (all valves) 94lb (42.638kg)
Outer Valve Spring Pressure - Closed (all valves) 49.6lb (22.498kg)
   
Camshaft  
Journal Diameter (Front) 1.6655 to 1.666in (42.304 to 42.316mm)
Journal Diameter (Centre) 1.62275 to 1.62325in (41.218 to 41.231mm)
Journal Diameter (Rear) 1.37275 to 1.3735in (34.87 to 34.88mm)
End Float 0.003 to 0.007in (0.076 to 0.178mm)
Bearings 3, steel-backed white metal
Bearing Inside Diameter (reamed in position)  

Front Bearing

1.667 to 1.6675in (42.342 to 42.355mm)
Centre Bearing
1.6245 to 1.6255in (41.261 to 41.287mm)
Rear Bearing
1.3745 to 1.3750in (34.91 to 34.92mm)
Running Clearance (Rear Bearing) 0.001 to 0.00225in (0.025 to 0.057mm)
Bearing Length (Rear Bearing) 49/64 +/- 0.010in (19.45 +/- 0.25mm)
   
Engine Lubrication  
Oil Pressure (normal running) 60psi (4.22kg/cm2) at 70 degrees C/158 degrees F oil temperature.
   
Cooling System  
Termostat temperature 82 degrees Celsius (180 degrees F)
   
Clutch  
Make and Type (Early) BMC single dry plate
Make and Type (Later) Diaphragm spring
Diameter 7.125in (180.9mm)
Facing Material (Standard) Wound yarn, riveted
Facing Material (Optional) Wound yarn, cemented and riveted
Pressure Springs (Early Type, Inner) 6
Pressure Springs (Early Type, Outer)

6

Colour (Inner) Green spot
Colour (Outer) White spot