3 replies to this topic

[mk3man]

I have a red (possibly painted by someone) 11 stud 12G940 head with the same sized valves as my 12G1805 mk3 S head but without the 1805 stamped into it behind the thermostat housing, also has double valve springs, any ideas what its off? 1300gt possibly

 

 cheers folks

[nicklouse]

Could be anything. It’s not like we did not add extra holes to heads for the extra stub and bolt. Though many just did it for two extra studs.

[gazza82]

From Keith Calver's site:

12G940 1.401"/35.6 1.15"/29.2 21.4 Stamped '12G1805' on flat area by thermostat - MG1300, 1300GT & Mk3 Cooper S
12G940* 1.401"/35.6 1.15"/29.2 21.4 As above plus MG Metro

*Note:
* A+ head castings - despite having the same 12G940 casting number - are considerably different in appearance, loosing the flat area behind the thermostat housing and around the rest of the rocker/head stud areas to a sculptured look - where these areas are replaced by a 'sunken' cast finish. The A+ castings were introduced with the appearance of the Metro in 1980, although some late 1275GTs (1979-on) had them fitted. Generally they are easily recognised by their colour - a putrid yellow on the small-bore castings and bright red on the large-bore ones, a paint finish that is VERY difficult to remove, even in a chemical tank.

* The MG Metro Turbo shares the same valve sizes with the other non-'big valve' 12G940 variants but has 8mm, sodium-filled exhaust valves.


https://www.calverst...casting-number/

[Spider]

As Nick said, it could be anything. It's a very common modification to make to these heads, Here in Aust. I'm actually having a lot of trouble finding standard small valve 12G940 heads now, so many have had big exhaust valves (and Inlets too) fitted and some questionable work done on the ports.

If it hasn't had the P/N stamped in to the thermostat area, then it's highly likely a modified head.