Morris Minor Owners Club Logo

Morris Minor Owners Club

Potteries Branch

Engine Information

There were four types of engine fitted to the Morris Minor.  Each one corresponds to the series of car. 

Series Engine Capacity Compression BHP Torque Bore Stroke 0-50 MPH Top speed
Series MM Sidevalve 918cc 6.6:1 27.5 @ 4400 RPM 39 lb/ft @ 2400 RPM 57mm 90mm 37.1 Sec 62 MPH
Series II A-series 803cc 7.2:1 30 @ 4800 RPM 40 lb/ft @ 2400 RPM 58mm 76mm 29.2 Sec 62 MPH
Series 3 A-series 948cc 8.3:1 37 @ 4750 RPM 50 lb/ft @ 2500 RPM 62.9mm 76.2mm 18.5 Sec 75 MPH
Series 5 A-series 1098cc 8.5:1 48 @ 5100 RPM 60 lb/ft @ 2500 RPM 64.6mm 83.7mm 15.8 Sec 78 MPH

Note:- Two designs of side valve engine were fitted to the Series MM:

Type USHM 2. Up to engine no. 77000

No oil filter on early engines. No thermostat

No water pump thermo syphon cooling

Dynamo attached to cylinder head

Type USHM 3.  Engine no 77001 on

Oil Filter. Thermostat in alloy housing

Blanking plate for optional water pump and heater

Alloy water jacket with dynamo attached

Engine drain tap when water pump fitted

Re designed cylinder head

Thermo syphon or water pump cooling

Gearbox / Rear Axle Information

ALL gearboxes fitted to the Morris Minor had synchromesh on 2nd, 3rd and top gears but not on bottom or reverse.

Series

Engine

Gearbox Type

Bottom

2nd

3rd

Top

Reverse

Diff ratio

Clutch

Series MM

Sidevalve

918cc

Cast Iron

3.95

2.31

1.54

1

3.95

4.55 (9/41) or optional 5.286 (7/37) or   5.375 (8/43)

6 1/4"

Spring

Series II

A-series

803cc

Aluminium alloy.  Smooth casing with no remote housing

4.09

2.588

1.679

1

5.174

5.286 (7/37)

6 1/4"

Spring

Series 3

A-series

948cc

Aluminium alloy.  Smooth casing with remote housing

3.628

2.374

1.412

1

4.664

4.55 (9/41)

6 1/4"

Spring

Series 5

A-series

1098cc

Aluminium alloy.  Ribbed casing with remote housing

3.628

2.172

1.412

1

4.664

4.22 (9/38)

7 1/4"

Spring

Midget A-series

1275cc

Aluminium alloy.  Ribbed casing with remote housing 3.2 1.916 1.357 1 4.114 3.9 (10/39) 6 1/2"

Diaphragm

NOTE:  The Midget gearbox information is included here for completeness but it was never factory fitted to a Morris Minor