Variation in port size on the 12g940 castings. Montego, Maestro, MG Metro
Turbo Mini Forums

Not so long ago I posted in a thread that the 1.3 Montego head was a slightly different casting to your normal 12g940

This is a snip from an article I just came across while looking for info on TAM 1059 &1061 valves

As a basis use a 1275 late metro casting '84 on to '89, all of these have the big 35.7mm inlet valve. These heads are also found on 1.3 maestros and 1.3 montegos. These larger valved heads already have a slightly bigger inlet port and throat to suit the bigger valve, so are different to the later unleaded and earlier small (33.3mm) inlet valve heads.

Now I have three heads at home 2 of which have had larger valves fitted the third is an MG head. All the valves are the numbers above. If I read that correct the MG Metro 1.3 Maestro and 1.3 Montego heads were cast with larger inlet ports but still numbered 12g940.

Own the day

The MG Metro head has a machined valve throat to suit the larger valve.

I believe that is the only difference.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The inlet valve was also reduced to 33.3mm on the later unleaded castings.

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