Somerford Mini Ltd. Ordering Parts Using This Catalogue

Cylinder Head - 1275cc (Not Cooper S)
No. Part No. Description Qty. Remarks No. Part No. Description Qty. Remarks
1275cc Cylinder Head Identification
Cylinder head details here are appropriate for the 1275cc engine in Mini 1275 GTs from 1969 to 1980,
Mini Coopers from 1990 onwards and standard Minis from 1992 on. The ‘eleven stud’ heads for 1275cc
Mini Cooper S engines are described in the next section of the Somerford Mini catalogue.
The cylinder head design for the non-Cooper S 1275cc Mini engine was shared with many other BMC/
Leyland/Austin Rover model engines, but unlike other A Series cylinder heads it was only ever fitted to
the one size of engine. Thus other cars sharing the cylinder head were all 1275cc models, including the
Austin/Morris 1300 (but not the high performance versions, which used the late Cooper S head), Morris
Marina and Ital 1.3, Austin Allegro 1300 and 1.3, Austin Healey Sprite Mk IV/MG Midget Mk III, Austin/MG
Metro, Austin Maestro and Montego. The number cast into the cylinder head is 12G940, but note that
there are several versions of cylinder head identified by this number, which means that care has to be
taken when sourcing a head to use on your Mini.
- CYLINDER HEAD, bare, with guides only 1 1275cc carburetter 1992-94; please
(late 12G940 casting)
contact us for details.
- CYLINDER HEAD, bare, with guides only 1 Multi and single point injection 1997
(late 12G940 casting)
on; please contact us for details.
Gasket Set
3 GEG103SMC GASKET SET, cylinder head 1 Carburetter models 1969-94.
GEG103SMI GASKET SET, cylinder head 1 Single and multi point injection 1991 on.
The cylinder head gasket set,also kno wn as a ‘decoke’ or ‘decarbonising’ set, includes the head gask et,
manifold gasket (standard in the carburetter gasket set, reinforced in the injection set), two thermostat
housing gaskets (one extra for engines with sandwich plates), HS2, HS4 and HIF carburetter gaskets
(carburetter gasket set only), rocker cover gasket, plus heater take-off gasket (carburetter gasket set only).
Valve stem oil seals are not included; please choose the ones you want and order them separately.
Different versions of 12G940 heads used either 1 5/16" (33mm) or 1 13/32" (35.6mm) inlet valves; 1
5/16" is the correct diameter for an inlet valve in an original non-Cooper S Mini engine (exhaust valves
are always 1 5/32" (29.4mm) diameter, whatever the application). Cooper S, high performance Austin/
Morris 1300 and MG Metro models somehow squeezed in the larger 1 13/32" diameter inlet valves.
Confusingly, the last Cooper S cylinder heads plus the aforementioned high performance 1300 heads are
still 12G940 castings, even though they have ‘eleven stud’ fixings to the cylinder block (standard 12G940s
are nine stud); they do however have an extra 12G1805 part number stamped by the thermostat housing
for extra identification. As mentioned above, these later Cooper S heads are detailed in the next section.
Late model 12G940 castings, used on 1990s Minis, can be distinguished by separate sculpted and
machined areas around the thermostat housing and heater take off, whereas the ear lier castings are
machined straight across from these areas to the rocker cover. Once again, care needs to be taken here:
do not assume that if you have identified a late casting it must be Mini specification. Metros also used
this casting with the heater take-off blank ed off (as was the take-off on fuel injection and 1992-94
carburetter Mini heads), and the MGs had the larger 1 13/32" inlet valves. Metro Turbos and ERA Mini
Turbos similarly used late type 12G940 heads, this time with Mini sized inlet valves - the valves are
however sodium filled and the deck of the cylinder head is thinner.
Lastly, mention should be made of the air injection cylinder head used on North American specification
(NAS) Austin Healey Sprite Mk IVs, MG Midget Mk IIIs and Austin Americas between 1968 and 1974. This
head casting, displaying part number 12G939, is a strengthened version of the 12G940 including air
injection ports for the NAS emission control systems. While on the face of it not strictly relevant to a
Mini parts catalogue, it is in all other respects a 12G940 head and because of its increased strength it
makes an ideal and reliable candidate for tuning treatment. Plenty of new 12G939 heads were still
around in the classic car par ts marketplace at the beginning of the 1990s and while it will not be easy,
you can find one even now if you want one.
At various times during A Series engine production, new and reconditioned cylinder heads from the
factory were either in ‘assembly’ or ‘bare’ condition. Assemblies usually included studs, valves, valve
springs and guides (but not rockers, rocker shaft and pedestals) whereas bare heads included valve guides
and studs or valve guides only. These states of build were however not hard and fast, so if you are
offered a new or reconditioned factory cylinder head on an exchange unit scheme you should establish
before ordering exactly what you will receive, to guard against the possibility of giving a way components
on your old head that you will still need in future!
Rebuilt or Repaired Cylinder Heads
Somerford Mini Ltd. offers a bespoke cylinder head rebuilding and repair service. In our experience, a
large number of customers require some degree of modification to their cylinder heads and as a result,
whether you want a standard head or one that is uprated to any degree, we ask you to contact us to
discuss your requirements. It would be helpful if you could also supply us with the details of your
engine: full engine number (if known) and type (capacity, high or low compression, gearbox, breathing
system, etc.), plus any existing modifications. The more you can provide us with, the better we can help
you. All of our cylinder heads are built to run on lead-free fuel, unless you specify otherwise.
Cylinder Head Components
Cylinder Head Fixings
4 GEG300 GASKET, cylinder head, copper 1
5 CAM150 STUD, cylinder head, long 4
6 CAM151 STUD, cylinder head, short 5/4 Qty. reduced 1990-96.
TAM1617 STUD, cylinder head and coil bracket 1 1990-96.
7 51K1193 NUT, cylinder head to block 9 1969-78 standard fitment.
8 PWZ106 WASHER, plain 9 1969-78 standard fitment.
GB126B WASHER, plain 9 Alternative heavy duty washer.
Withstands up to 80lbf ft torque.
9 CAM4545 NUT, flanged, cylinder head to block 9 1978 on standard fitment.
(does not require plain washer) 1969-78 heavy duty alternative.
CAM4545 NUT,flanged, coil bracket to head stud 1 1990-96.
Plugs and Adaptors
10 2K1345 PLUG, oil hole, cylinder head 1 1969-80, alternative.
6K808 PLUG, oil hole, cylinder head 1 1969-80, alternative.
11 CDU2601 RIVET, oil hole, cylinder head 1 1990-96.
LYQ100050 RIVET, oil hole, cylinder head 1 1997 on.
12 12G2092 PLUG, water hole 3 1969-96.
154545A PLUG, water hole 3 1997 on.
13 AEA771 PLUG, water and dowel hole 2
14 12G3503 PLUG, cleaning hole 2 1969-96.
15 12A2075 ADAPTOR, by-pass hose, long 1 1969-80 and 1275cc carburetter
models 1992-94.
Thermostat Housing and Fixings
16 - HOUSING, thermostat 1
For details of thermostat housings, please see the ‘Cooling - Thermostats and Water Pumps’ section in the
Cooling and Heating area of the Somerford Mini catalogue.
17 GTG101 GASKET, thermostat housing, cork 1/2 Qty. 2 required 1990 on.
GUG705558 GASKET, thermostat housing, paper 1/2 Qty. 2 required 1990 on.
In theory the two gasket materials are interchangeable, but the cork gasket seems to be preferred by
Somerford Mini customers for a simple thermostat housing fitment, whereas the later paper gasket is
preferred for a thermostat housing with sandwich plate (applicable for 1990 on).
18 CHS2515 STUD, thermostat housing 3 1969-80 (carburetter models).
CHS2524 STUD, thermostat housing/sandwich plate 3 1990-91 (carburetter models).
19 FNZ105 NUT 3 1969-91 (carburetter models).
20 PWZ105 WASHER, plain 3 1969-91 (carburetter models).
21 DAM7760 BOLT, thermostat housing/sandwich plate 3 1991 on (injection and 1992-94
carburetter models).
1 - CYLINDER HEAD ASS’Y, with valves 1 1275 GT 1969-80; please contact us
(early 12G940 casting)
for details.
- CYLINDER HEAD ASS’Y, with valves 1 Cooper carburetter 1990-91; please
(late 12G940 casting)
contact us for details.
- CYLINDER HEAD ASS’Y, with valves 1 Single point injection 1991-96; please
(late 12G940 casting)
contact us for details.
- CYLINDER HEAD ASS’Y, with valves 1 1275cc carburetter 1992-94; please
(late 12G940 casting)
contact us for details.
- CYLINDER HEAD ASS’Y, with valves 1 Multi and single point injection 1997
(late 12G940 casting)
on; please contact us for details.
2 - CYLINDER HEAD, bare, with guides and 1 1275 GT 1969-80; please contact us
studs only (ear ly 12G940 casting) for details.
- CYLINDER HEAD, bare, with guides only 1 Cooper carburetter 1990-91; please
(late 12G940 casting)
contact us for details.
- CYLINDER HEAD, bare, with guides only 1 Single point injection 1991-96; please
(late 12G940 casting)
contact us for details.
Heater Valve and Fixings
1275 GT 1969-80
22 - VALVE, heater 1 See note below.
For details of the heater valves, please see the ‘Heating - Heater Hoses, Water Control Valves and Cables’
section in the Cooling area of the Somerford Mini catalogue.
23 88G221B GASKET, heater valve 1
24 53K402 STUD, heater valve 2
25 FNZ104 NUT 2
26 LWZ304 WASHER, locking 2
Heated Manifold Adaptor and Fixings
Cooper Carburetter 1990-91
27 12G2534 ADAPTOR, heated manifold take-off 1
28 88G221B GASKET, adaptor to cylinder head 1
29 TAM1368 SCREW, adaptor to cylinder head 2
Tel. 01249 721421 Fax. 01249 721316 www.somerford-mini.co.uk
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