6 replies to this topic

[Mini_the_Minx]

Model: 1275 GT bored out
Year: 1970's
Description of problem (please be as in depth as possible): On my cylinder head its stamped with the code 12G895 'S' directly behind the thermostat housing and 12G940 is cast behind the rockers. I'm trying to identify it but i can't find any info anywhere. Does anyone have any idea what this is?

[Asphalt]

12G940 is a 1275 head. I don't know what the 12G895 stands for, probably some indication of manufacturing (faundry?).

There are many, partly very different, heads with that number; actually all but eraly Cooper 'S' heads have the 12G940 number. Some of them have larger inlet valves (36mm vs. 33mm std.), 11 or 9 holes for head studs, and two shapes: A- and A+. A- has a 'flat' surface, A+ has a 'structured' surface. See here.

And late A+ heads (injection era) have no hole for the temp. sender and no heater take off. A+ heads usually don't have a waterpump bypass.

So basicly - it could be everything

[Nightrain]

Are you sure it's not 12G1805 ? Is it 11 Stud ? In which case it would be a Mk3 S head.

[Mini_the_Minx]

It may very well be a 1805 and it is an 11stud. Have you got any info on that engine Nightrain?

[Nightrain]

The Mk3 S engine was also fitted to the Austin/Morris 1300GT's and the MG1300. As well as the slightly better head, they also got better crankshaft made from EN16T. Cooper S conrods which again where made from slightly better but heavier steel to match the smaller big end of the S crank. They came fitted with Twin HS2's, the S's 3 into 1 exhaust manifold and exhaust.

[Guess-Works.com]

The ADO16 ( Austin 1300GT ) engines wern't cooper S, similar but ran a 1.75" bigend journal, with GT rods, not S rods ( and the crank was more akin to the GT crank than the S crank in material).... But did use the same mk3 cooper S head, 11 stud, but with a 1.15" exhaust valve instead of the 1.21" used on the MK1/2 Cooper S AEG* heads.

Does sound like a 1300 GT head, and there's nothing wrong with them..

[Nightrain]

Proper S's ie. Mk1 & 2 had cranks made from EN40B steel, the later Mk3 S had a 1 5/8" big end these cranks where EN16T. Later on they change again, to 1 3/4" with another down grade in material.