15 replies to this topic

[Dan]

12G940 is just a casting number, a reference number for the tool the bare head is cast from. A great many different specification heads have been carved from this basic lump of iron over the years. Some leaded, some unleaded, some good others not so good.

As above there isn't a lot of difference between A series and A+ engines. If you want details then there are many pages of the forum devoted to this subject, the search tool will reveal all you need to know. There are a few specific parts that cannot be swapped from one to the other but ultimately transverse Mini / Metro A+ and A series are the same engine. The A+ is just a refinement of the original because it was very old and advances had been made along with a different basic set of anciliaries being used from when it was deisgned originally (alternator replacing dynamo for example) which all demanded changes. Heads are basically interchangeable, but may foul water pump pulleys (which can be changed). Some people say one block is preferable in an engine build whereas other people will choose the other. It is very likely that your engine will be an A+.

1293 is the first standard oversize on the 1275 engine, using +20 thou pistons. You could stick with that or you could go much larger and you don't have to compromise reliability for this. Reliability has a lot to do with the quality of components and the actual engine build and design. If you design an engine using poorly matched parts chosen for bling value rather than engineering, build it sloppily and don't look after it then it will be unreliable. Even 1380s can be built to be very reliable daily drivers.

Why not try a 1330 with a good cam which will deliver nice torque without being a bag of spanners at idle. A well made head from a good supplier using quality valves and springs (which should be correct to match the cam) is essential. Fuelling that meets the engine's needs without being over the top and a bullet proof ignition system. Good quality cooling. That's the sort of thing I'd go for anyhow, exactly what you build is up to you.