Tuning Data for Your Classic Mini Cooper Engine

 

The tables below shows the factory tuning specifications for the various models of Mini Cooper engines including:
Mini Cooper 997cc (1961-64)
Mini Cooper 998cc (1964-69)
Mini Cooper S 970, 1071cc (1963 - 65)
Mini Cooper S 1275cc (1964-71)

If your engine is modified, these settings may no longer be valid or provide safe operation of your engine.

These specifications are those as given by British Leyland at approximately the end of Mini Cooper S production in 1971. Older Mini Coopers may have been fitted with alternative spark plugs, ignition coils, and carburettor spring/jet/needle; if restoring to original condition concours points may be increased by consulting Original Mini Cooper and Cooper S by John Parnell for the exact original equipment.

Mini Cooper 997cc (1961-64)

Engine  
Type 9F
Capacity 997cc (60.87 cu in)
Compression ratio (High) 9:1
Compression ratio (Low) 8.3:1
Firing order 1,3,4,2
Idling speed (approx) 500 rpm
Fast idle 900 rpm
Ignition timing (static, high CR) 7 degrees BTDC
Ignition timing (static, low CR) 5 degrees BTDC
Ignition timing (600 rpm, high CR) 9 degrees BTDC
Ignition timing (600 rpm, low CR) 7 degrees BTDC
Timing marks Dimples on timing wheels, marks on flywheel.
Valve rocker clearance 0.012 in (0.305mm) cold.
   
Distributor  
Type Lucas 25D4
Rotation of rotor Anti-clockwise
Dwell 60 +/- 3 degrees
Contact breaker gap 0.014 to 0.016 in (0.35 to 0.4mm)
Condenser capacity 0.18 to 0.24 micro-farads
Serial number 40774 (high CR), 40873 (low CR)
   
Centrifugal Advance (High CR)  
Decelerating check, vacuum pipe disconnected
  • 16 to 22 degrees at 1600 rpm
  • 2 to 8 degrees at 1000 rpm
  • 0 to 3 degrees at 800 rpm
No advance below 600 rpm
   
Centrifugal Advance (Low CR)  
Decelerating check, vacuum pipe disconnected
  • 26 to 30 degrees at 2600 rpm
  • 21 to 25 degrees at 2000 rpm
  • 15 to 19 degrees at 1200 rpm
  • 8 to 12 degrees at 900 rpm
  • 0 to 5 degrees at 600 rpm
No advance below 300 rpm
   
Vacuum Advance (High CR)  
Starts 3 in (7.62 cm) Hg
Finishes 14 degrees at 8 in (20.3 cm) Hg
   
Vacuum Advance (Low CR)  
Starts 4 in (10.1 cm) Hg
Finishes 14 degrees at 7 in (17.7 cm) Hg
   
Spark Plugs  

Type

Champion
Type N5
Gap 0.025 in (0.625 mm)
   
Ignition Coil  
Type Lucas HA12
Primary resistance at 20 degrees C 3.0 to 3.4 ohms (cold)
Current consumption 3.9 amps
   
Carburetors  
Type Twin SU HS2
Piston spring Red
Jet size 0.090 in (2.29mm)
Needle (standard) GZ

Mini Cooper 998cc (1964-69)

Engine  
Type 9FA
Capacity 998cc (60.96 cu. in)
Compression ratio (High) 9:1
Compression ratio (Low) 7.8:1
Firing order 1,3,4,2
Compression Pressure (High) 165 psi (11.6 kg/cm2)
Compression Pressure (Low) 150 psi (10.5 kg/cm2)
Idling speed (approx) 500 rpm
Fast idle 900 rpm
Ignition timing (static, high CR) 5 degrees BTDC, 91 to 96 octane
Ignition timing (static, low CR) 5 degrees BTDC
Ignition timing (600 rpm, high CR) 7 degrees BTDC
Ignition timing (600 rpm, low CR) 7 degrees BTDC
Timing marks Dimples on timing wheels, marks on flywheel.
Valve rocker clearance 0.012 in (0.305mm) cold.
   
Distributor  
Type Lucas 24D4
Rotation of rotor Anti-clockwise
Dwell 60 +/- 3 degrees
Contact breaker gap 0.014 to 0.016 in (0.35 to 0.4mm)
Condenser capacity 0.18 to 0.24 micro-farads
Serial number 40955, 41032 (high CR), 40958, 41031 (low CR)
   
Centrifugal Advance (High CR)  
Decelerating check, vacuum pipe disconnected
  • 30 to 34 degrees at 6000 rpm
  • 28 to 32 degrees at 5400 rpm
  • 24 to 28 degrees at 4200 rpm
  • 18 to 22 degrees at 2300 rpm
  • 12 to 16 degrees at 1800 rpm
  • 1 to 5 degrees at 800 rpm
No advance below 300 rpm
   
Centrifugal Advance (Low CR)  
Decelerating check, vacuum pipe disconnected
  • 28 to 32 degrees at 5500 rpm
  • 26 to 30 degrees at 4400 rpm
  • 22 to 26 degrees at 2200 rpm
  • 16 to 20 degrees at 1800 rpm
  • 3 to 9 degrees at 1000 rpm
  • 0 to 3 degrees at 600 rpm
No advance below 400 rpm
   
Vacuum Advance (High CR)  
Starts 3 in (7.62 cm) Hg
Finishes 14 degrees at 8 in (20.3 cm) Hg
   
Vacuum Advance (Low CR)  
Starts 3 in (7.62 cm) Hg
Finishes 16 degrees at 7 in (17.7 cm) Hg
   
Spark Plugs  

Type

Champion
Type N5
Gap 0.025 in (0.625 mm)
   
Ignition Coil  
Type Lucas HA12
Primary resistance at 20 degrees C 3.0 to 3.4 ohms (cold)
Current consumption 3.9 amps
   
Carburetors  
Type Twin SU HS2
Piston spring Blue
Jet size 0.090 in (2.29mm)
Needle (standard) GZ
Needle (rich) M
Needle (weak) GG

 

Mini Cooper S 970, 1071cc (1963 - 65)

Engine  
Type 9FC, 10F
Capacity 970cc/59.1 cu in, 1071cc/63.35 cu in
Compression ratio (970cc) 10:1
Compression ratio (1071cc) 9:1
Firing order 1,3,4,2
Compression Pressure (High) 190 to 200 psi (13.36 to 14.07 kg/cm2)
Idling speed (approx) 600 rpm (approx)
Fast idle 1000 rpm
Ignition timing (static, 970cc) 12 degrees BTDC
Ignition timing (static, 1071cc) 3 degrees BTDC
Ignition timing (600 rpm, 970cc) 14 degrees BTDC
Ignition timing (600 rpm, 1071cc) 5 degrees BTDC
Timing marks Dimples on timing wheels, marks on flywheel.
Valve rocker clearance 0.012 in (0.305mm) cold, 0.015 in (0.38mm) for competition.
   
Distributor  
Type Lucas 23D4 (no vacuum advance)
Rotation of rotor Anti-clockwise
Dwell 60 +/- 3 degrees
Contact breaker gap 0.014 to 0.016 in (0.35 to 0.4mm)
Condenser capacity 0.18 to 0.24 micro-farads
Serial number 40819
   
Centrifugal Advance  
Decelerating check, vacuum pipe disconnected
  • 28 to 32 degrees at 7000 rpm
  • 22 to 26 degrees at 5200 rpm
  • 10 to 14 degrees at 1600 rpm
  • 6 to 12 degrees at 1000 rpm
  • 0 to 3 degrees at 600 rpm
No advance below 450 rpm
   
Spark Plugs  

Type

Champion
Type N9Y
Gap 0.025 in (0.625 mm)
   
Ignition Coil  
Type Lucas HA12
Primary resistance at 20 degrees C 3.0 to 3.4 ohms (cold)
Current consumption 3.9 amps
   
Carburetors  
Type Twin SU HS2
Piston spring Red
Jet size 0.090 in (2.29mm)
Needle (970cc) AN
Needle (1071cc) H6

 

Mini Cooper S 1275cc (1964-71)

Engine  
Type
  • 12FA (Mk1, 2)
  • 12H (Mk3)
Capacity 1275 cc (77.9 cu. in)
Compression ratio (970cc) 9.71:1
Compression ratio (1071cc) 9:1
Firing order 1,3,4,2
Compression Pressure (High) 190 to 200 psi (13.36 to 14.07 kg/cm2)
Idling speed (approx) 600 rpm (approx)
Fast idle 1000 rpm
Ignition timing (static) 2 degrees BTDC
Ignition timing (600 rpm) 4 degrees BTDC
Timing marks Dimples on timing wheels, marks on flywheel.
Valve rocker clearance 0.012 in (0.305mm) cold, 0.015 in (0.38mm) for competition.
   
Distributor  
Type Lucas 23D4 (no vacuum advance)
Rotation of rotor Anti-clockwise
Dwell 60 +/- 3 degrees
Contact breaker gap 0.014 to 0.016 in (0.35 to 0.4mm)
Condenser capacity 0.18 to 0.24 micro-farads
Serial number 40819, 41033
   
Centrifugal Advance  
Decelerating check, vacuum pipe disconnected
  • 28 to 32 degrees at 7000 rpm
  • 22 to 26 degrees at 5200 rpm
  • 10 to 14 degrees at 1600 rpm
  • 6 to 12 degrees at 1000 rpm
  • 0 to 3 degrees at 600 rpm
No advance below 450 rpm
   
Spark Plugs  

Type

Champion
Type N9Y
Gap 0.025 in (0.625 mm)
   
Ignition Coil  
Type Lucas HA12
Primary resistance at 20 degrees C 3.0 to 3.4 ohms (cold)
Current consumption 3.9 amps
   
Carburetors  
Type Twin SU HS2
Piston spring Red
Jet size 0.090 in (2.29mm)
Needle (standard) M
Needle (rich) AH2
Needle (weak) EB