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: 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 |
|
No advance below | 600 rpm |
Centrifugal Advance (Low CR) | |
Decelerating check, vacuum pipe disconnected |
|
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 |
|
No advance below | 300 rpm |
Centrifugal Advance (Low CR) | |
Decelerating check, vacuum pipe disconnected |
|
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 |
|
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 |
|
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 |
|
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 |