Basically it seems Maestros had the following heads:
| Year | Head Number | Valves | Fuel | Info |
| 1983-84 | 12G940 | 33/29mm | leaded | - |
| 1984-89 | 12G940 | 36/29mm | leaded | From engine numbers 12H999104761 and 804102434 |
| 1983-84 | 12G940 | 33/29mm | leaded | Except the dreadful 3+E economy Maestro which retained the small valve 12G940, and its concept of 3 gears + over drive inspired the TPi Cooper. |
| 1989-94 | 12G940 | 33/29mm | unleaded | - |
Although a replacement in the form of the Rover 214/216 appeared in 1989, the maestro continued in production in 1275 form as a budget car.
After 1990 only the Mini and the Maestro used the 1275 engine.
Another bone of contention is the unleaded MG Metro. Some claim it used an unleaded 36/29mm 12G940. Tuning writer Des Hammill says all unleaded 12G940's were the smaller 33/29mm. I think he is right. In 1989 the A-series engine became a low volume product as Rover moved over to the new K-series,and spending money on an old engine couldn't be justified.
It has been claimed that the 1990 Mini Cooper had the MG Metro engine.With 61bhp compared with 72bhp it quite clearly did not!
Info from Ian gleaned from the Haynes Maestro Manual, added 12/02/02.
07 June 2003