External Engine - 1275 (not cooper s)

1275cc Engine Identification
The first application of the 1275cc A Series engine in the Mini was in 1964, with the advent of the 1275 Mini Cooper S. This particular engine was however a very different animal to the 1275cc engine described on this page; for the Cooper S unit, please refer to the 'External Engine - 970, 1071 and 1275cc (Cooper S)' section of the Somerford Mini catalogue.

The engine described here made do without the eleven stud cylinder head and many other Cooper S engine attributes and did not have tappet chest covers on the bulkhead side of the engine block - for this reason it is often referred to as the 'solid wall block' 1275cc engine. Its first and only use in a Mini for just over ten years was in the 1275 GT model, introduced in 1969 and phased out in 1980. During this period the engine was subject to a number of modifications, not least of which were the change from twin or 'duplex' to single or 'simplex' timing chain in 1974 and the gradual introduction of 'A Plus' features at the end of the 1970s. Although not programmed for fitment in a Mini bodyshell through the 1980s, the 1275cc engine was destined for considerable use in the Austin Metro; for this reason most A Plus modifications were present by the time of the 1275 GT's demise, including the characteristically ribbed (much stronger) cylinder block with its completely revised distributor mounting.

For the next ten years the Mini soldiered on without a 1275cc variant and the factory declined to put a genuine performance Mini in the showroom line up (customers being encouraged to look at the MG Metro instead), despite the popularity of 998cc Mini limited editions like Flame and Racing with their obvious Mini Cooper styling cues. Finally in 1990 came the new Mini Cooper, complete with a fully-fledged A Plus 1275cc engine (borrowed ironically from the MG Metro). This was however a very different (lead-free fuelled, with catalytic converter) power unit to that seen in the 1275 GT ten years earlier, having been emasculated to a degree by emission control regulations. The process of loading up the engine with more and more regulations-compliant equipment continued through the 1990s, the major milestones being the phased replacement of the carburetter by single point injection (SPi) from 1991 and a significant overhaul of the power unit design coinciding with the introduction of multi point injection (MPi) model in 1997. The 1997 on engine, in both MPi and Japan-only SPi guises, is immediately recognisable by the lack of a distributor, or any facility to attach one! Meanwhile, by 1992, 1275cc had become the only engine capacity available in the Mini line up (the lower-powered 998cc unit could no longer cope with all the extra equipment) and that was the way things stayed until the end of Mini production in 2000. Amongst other things this meant that to continue to be able to offer an automatic gearbox option, an automatic type 1275cc engine was produced for the Mini from 1992.

Other applications of the transverse 1275cc A Series included the BMC 1100/1300, commonly referred to as the 'ADO16' range. Higher performance engines from such models as the MG 1300 and Austin/Morris 1300 GT in the ADO16 range were frequently to be found transplanted into Minis by enthusiasts; particularly in favour was the 11 stud head engine, which is not the same as a Cooper S unit, by the way. Several other Leyland and Austin Rover cars also used the 1275cc engine, including the Allegro, overseas-built Mokes and the Maestro/Montego models (the latter featuring a different transmission which rendered Mini transplants impossible). The 1980s Metro's 1275cc unit proved to be the most popular with Mini owners who desired an easy performance upgrade, the whole engine/transmission assembly less manifolds fitting comfortably in a Mini with very few necessary modifications. For this reason, if you see an engine from another car under the bonnet of a Mini nowadays, it is most likely to be one from an MG Metro or its short-lived predecessor, the Austin Metro 1.3 S.

Engine serial number prefix codes are important in identifying what you have in your car and establishing which replacement parts to fit to it. The 1275cc engine number prefixes used on non-Cooper S Mini engines are listed here for that reason. The engine serial number is stamped on a plate affixed to the cylinder head mating face or 'deck' of the cylinder block, at the front of the engine towards the right hand side, as you look at the engine in the car. Note that the last code letter before the serial number itself on pre-A Plus engines always relates to the compression ratio of the engine: H for high compression, L for low compression. A Plus high or standard (as 'low' was then known) compression engines are by contrast identified by the letter plus two numbers part of the engine serial number prefix; a full list of these is shown below.

Factory reconditioned engines always lost their serial numbers in favour of an engine number plate stamped with the appropriate part number for the intended application for each engine. In the absence of an engine serial number on a factory reconditioned unit, this is the only means of identification - but beware! Factory reconditioned engines were more often than not built up with whatever suitable components were to hand; for example, new parts were usually plucked from the engine production line and were therefore of the latest design. Reused components came from stocks of parts which would do the same job, but were not necessarily the same design, all lumped together. In other words, parts used in the rebuild were frequently incorrect in a historic sense for the engine being rebuilt.

1275cc Mini Engine Serial Number Prefix Codes (not Cooper S) 1969-80
12H/389	1275 GT manual gearbox engine with remote gearchange, rubber coupling drive shafts and dynamo (1969-73).
12H/390	1275 GT manual gearbox engine with remote gearchange, rubber coupling drive shafts and alternator (1969-73).
12H/706	1275 GT manual gearbox engine with rod gearchange, 'pot' joint drive shafts and alternator (1973-80).
12H/831	1275 GT manual gearbox engine, as per 12H/706 but Police specification (1974-80).
A Plus cylinder blocks were used from engine number 12H/706/-/026400 onwards.

1275cc Mini A Plus High Compression Ratio (10:1) Engine Serial Number Prefix Codes 1990-96
12H/-/F53	Manual gearbox engine for carburetter, with 3.105:1 final drive and oil cooler (1990-91).
12H/-/G01	Manual gearbox engine for carburetter, with 3.105:1 final drive; without oil cooler (1990-91).
12H/-/F77	Manual gearbox engine for SPi, with 3.21:1 final drive (1991-93).
12H/-/J02	Manual gearbox engine for SPi, with 3.21:1 final drive (1994-96).
12H/-/J66	Manual gearbox engine for SPi, with 3.21:1 final drive and 55 amp uprated alternator (1996).
12H/-/J77	Manual gearbox engine for SPi, with 3.21:1 final drive, 55 amp uprated alternator and air conditioning (Japan, 1995-96).
12H/-/J18	Manual gearbox replacement engine with cylinder head, for SPi (1991-96).
12H/-/J13	Manual gearbox replacement engine without cylinder head, for SPi (1991-96).

1275cc Mini A Plus Standard Compression Ratio (9.4:1) Engine Serial Number Prefix Codes 1992-96
Note that while standard compression ratio engines were generally non-Cooper units, some export markets did receive Coopers with standard compression ratio engines. Moreover, small numbers of Coopers with automatic gearboxes were built for export, too. This explains the 1992 start date for standard compression ratio SPi manual and automatic engines; these engines only started to be seen in UK (and most European markets) cars from 1994.
12H/-/G03	Manual gearbox engine for carburetter, with 3.105:1 final drive (1992-93).
12H/-/J04	Manual gearbox engine for carburetter, with 3.105:1 final drive (1993-94).
12H/-/G04	Manual gearbox engine for carburetter, with 2.76:1 final drive (France, 1992-93).
12H/-/J05	Manual gearbox engine for carburetter, with 2.76:1 final drive (France, 1993-94).
12H/-/F75	Manual gearbox engine for SPi, with 3.105:1 final drive (1992-93).
12H/-/J01	Manual gearbox engine for SPi, with 3.21:1 final drive (1994-96).
12H/-/J21	Manual gearbox replacement engine with cylinder head, for carburetter (1992-94).
12H/-/J19	Manual gearbox replacement engine with cylinder head, for SPi (1992-96).
12H/-/J14	Manual gearbox replacement engine without cylinder head, for carburetter or SPi (1992-96).
12H/-/G05	Automatic gearbox engine with carburetter (1992-93).
12H/-/J06	Automatic gearbox engine with carburetter (1993-94).
12H/-/F76	Automatic gearbox engine with SPi (1992-94).
12H/-/J03	Automatic gearbox engine with SPi (1994-96).
12H/-/J92	Automatic gearbox engine with SPi and 2.76:1 final drive ( France, 1994-96).
12H/-/J20	Automatic gearbox replacement engine with cylinder head, for SPi (1992-96).
12H/-/J15	Automatic gearbox replacement engine without cylinder head, for carburetter or SPi (1992-96).

1275cc Mini A Plus High Compression Ratio (10:1) Engine Serial Number Prefix Codes 1997-2000
12H/-/K70	Manual gearbox engine for MPi, with 2.76:1 final drive (1997-2000).
12H/-/K71	Manual gearbox engine for SPi, with 3.21:1 final drive and air conditioning (Japan, 1997-1999).
12H/-/L13	Manual gearbox replacement engine with cylinder head, for MPi (1997-2000).
12H/-/L16	Manual gearbox replacement engine with cylinder head, for SPi (Japan, 1997-1999).
12H/-/L21	Manual gearbox replacement engine without cylinder head, for MPi or SPi (1997-2000).

1275cc Mini A Plus Standard Compression Ratio (9.4:1) Engine Serial Number Prefix Codes 1997-2000
12H/-/K72	Automatic gearbox engine for SPi, with air conditioning (Japan, 1997-1999).
12H/-/L14	Automatic gearbox replacement engine with cylinder head, for SPi, with air conditioning (Japan, 1997-1999).
12H/-/L15	Automatic gearbox replacement engine without cylinder head, for SPi, with air conditioning (Japan, 1997-1999).

Leyland/Unipart/Rover Mini 1275cc (not Cooper S) Reconditioned Engine Part Numbers
8G200	Manual gearbox engine, twin 'duplex' timing chain (1969-74).
38G527	Manual gearbox engine, single 'simplex' timing chain, with timing chain tensioner (1974-79).
BHM1220	Manual gearbox engine, single 'simplex' timing chain, with timing chain tensioner, A Plus block (1980).
RKM1112	Manual gearbox engine; later 'Silver Seal' part number. Specification as 8G200 (1969-74).
RKM1130	Manual gearbox engine; later 'Silver Seal' part number. Specification as 8G200; replaced RKM1112 (1969-74).
RKM1152	Manual gearbox engine; later 'Silver Seal' part number. Specification as 38G527 or BHM1220 (1974-80).
LBB10399	Manual gearbox engine, A Plus, high compression, carburetter (1990-91).
LBB10476	Manual gearbox engine, A Plus, high compression, SPi (1991-96).
LBB10479	Manual gearbox engine, A Plus, standard compression, carburetter (1992-94).
LBB10477	Manual gearbox engine, A Plus, standard compression, SPi (1992-96).
LBB10480	Automatic gearbox engine, A Plus, standard compression, carburetter (1992-94).
LBB10478	Automatic gearbox engine, A Plus, standard compression, SPi (1992-96).
LBB109070 Manual gearbox engine, A Plus, high compression, MPi (1997-2000).
LBB109080 Manual gearbox engine, A Plus, high compression, SPi (1997-2000).
LBB109090 Automatic gearbox engine, A Plus, standard compression, SPi (1997-1999).

Rebuilt or Repaired 1275cc Engine Assemblies
Somerford Mini Ltd. offers an engine rebuilding and repair service, courtesy of its workshop facility. We can carry out repairs or rebuilds on late-model engines, but the extent of rebuilding on an early engine is governed by - and sometimes restricted by - parts availability. Please contact us to discuss your Mini engine requirements - it would be helpful if you could supply us not only the details of what's gone wrong with your engine, but also the full engine number (if known) and type (capacity, high or low compression, gearbox, breathing system, etc.). The more you can provide us with, the better we can ascertain how we might possibly help you.

Gasket Sets
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
1	GUG49	GASKET SET, conversion ('bottom end set')	1	Manual gearbox models.
	LVQ701604EVA	GASKET SET, conversion ('bottom end set')	1	Automatic gearbox models.
Conversion gasket sets (often called 'bottom end' or 'supplementary' sets) include gaskets for the following: water pump, front cover, front mounting plate, oil pump, oil filter head, engine to gearbox joint and flywheel/torque converter housing. Washers, seals and O rings are included for the following: priming plug, drain tap/plug, main bearing cap, front cover, distributor housing and oil suction pipe.
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
	EGS001	GASKET SET, full engine	1	Manual gearbox carburetter models.
	EGS002	GASKET SET, full engine	1	Manual gearbox injection models.
A full engine gasket set includes the conversion gasket set listed above plus a cylinder head gasket set ('decoke' or 'decarbonising' set) minus the head gasket itself, which should be purchased separately according to the engine size.

External Engine Components
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
2	AEC876	PLUG, core (welch), cylinder block, 1 3/8" dia.	5/4	Qty. reduced from 1997 on.
3	2K1345	PLUG, oil pressure release valve passage	2	1969-80.
	TAM2009	PLUG, oil pressure release valve passage	2	1990 on.
For owners with 1980s 1275cc Austin or MG Metro engines in their Minis, please note that the TAM2009 plugs were introduced on these engines in 1985.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
4	12H1734	PLUG, oil gallery, solid brass	2	1969-80; not A Plus cylinder block.
	CAM4133	PLUG, oil gallery, cup type	4	1980-96; A Plus cylinder block.
	LYQ100120	PLUG, oil gallery	5	1997 on.
5	RU612123	RIVET, oil way	2	1990-96.
	LYQ100080	RIVET, oil way	1	1997 on.
6	ADP210	PLUG, oil feed	1	Automatic gearbox.
7	1B3664	WASHER, sealing	1	Automatic gearbox.
8	1A1964	RESTRICTOR, cam bearing oil feed	1	1969-96.
	TAM2056	RESTRICTOR, cam bearing oil feed	1	1997 on.
9	CAM150	STUD, cylinder head, long	4
10	CAM151	STUD, cylinder head, short	5/4	Qty. reduced 1990-96.
	TAM1617	STUD, cylinder head and coil bracket	1	1990-96.
11	CHS2515	STUD, fuel pump drive aperture	2	1969-94, carburetter models.
12	2A265	PLATE, blanking fuel pump drive aperture	1	1991-96, SPi models.
13	GUG705557GM	GASKET, blanking plate	1	1991-96, SPi models.
14	SH505061	SCREW, blanking plate to block	2	1991-96, SPi models.
15	LWZ205	WASHER, locking	2	1991-96, SPi models.
16	53K615	STUD, oil filter head	2	1969-73, manual gearbox. For paper element oil filters.
	CHS2613	STUD, oil filter head	2	1973-92, manual gearbox. For 'spin on' cartridge oil filters.
Note that from 1992-96 the oil filter head was attached with bolts rather than studs. Full details of all oil filter systems and their attachments can be found in the 'Oil Filter and Pipes' section of the Somerford Mini Catalogue.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
17	22A1203	PLATE, blanking cylinder block oil filter face	1	Automatic gearbox.
18	88G402	GASKET, blanking plate	1	Automatic gearbox.
19	SH506071	SCREW, blanking plate to block	2	Automatic gearbox.
20	12G1058	WASHER, sealing	2	Automatic gearbox.
21	12G1398	SCREW, main bearing cap to block	6
22	12G1268	DOWEL, main bearing cap	6
23	BHM1210	LINER SET, camshaft bearings	1	Manual gearbox.
	BHM1211	LINER SET, camshaft bearings	1	Automatic gearbox.
24	LDT100030	PLUG, blanking cam sensor	1	1997 on, SPi models.
25	LYX100320	O RING, blanking plug	1	1997 on, SPi models; included with blanking plug.
26	FS106161	SCREW, plug to block	1	1997 on, SPi models.
27	WC600041	WASHER, plain	1	1997 on, SPi models.
28	53K2853	PLUG, cooling system drain	1	1969-96.
29	6K638B	WASHER, sealing plug	1	Use with drain plug.
30	3H576	TAP, cooling system drain	1	1969-96, alternative to plug (not std. fitment).
31	2K4954B	WASHER, fibre, drain tap	A/R	Use with drain tap.
This washer not only seals the tap to the block, but also is intended (using whatever quantity is necessary) to shim the tap so that when tightly screwed to the block the spout faces downwards.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
32	12A1136	HOUSING, distributor	1	1969-80; not A Plus cylinder block.
33	13H2792	O RING, housing	1	1969-80; not A Plus cylinder block.
34	SH604061	SCREW, housing to block	2	1969-80; not A Plus cylinder block.
35	LWZ404	WASHER, shakeproof	2	1969-80; not A Plus cylinder block.

Engine Front Mounting Plate
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
36	AEG161	PLATE, engine front mounting	1	1969-74; for 'duplex' timing chain.
37	12G2626	PLATE, engine front mounting	1	1974 on; for 'simplex' timing chain and tensioner.
38	12G619B	GASKET, plate to block	1	1969-74; for 'duplex' timing chain.
	GUG705554GM	GASKET, plate to block	1	1974 on; for 'simplex' timing chain and tensioner.
39	SH605051	SCREW, plate to block	2
40	LWZ305	WASHER, locking	2
41	AEA687	SCREW, plate to main bearing cap	2	1969-74; 'duplex' timing chain.
42	53K2016	SCREW, plate to main bearing cap	2	1974 on; 'simplex' timing chain and tensioner.
43	WF600041	WASHER, shakeproof	2	1974 on; 'simplex' timing chain and tensioner.
44	AHU2379	PLATE, camshaft locating	1
45	SH604061	SCREW, plate to block	3	1969-96.
46	WF600040	WASHER, shakeproof	3	1969-96.
47	TAM1173	SCREW, plate to block	3	1997 on.

Timing Cover 1969-74 ('duplex' chain without tensioner pad)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
48	12G2506	COVER, front, timing, without oil separator	1	1969-71; includes oil seal.
49	12G2507	COVER, front, timing, with oil separator	1	1971-74; includes oil seal.
50	88G561	OIL SEAL, timing cover	1	Included in timing covers.
51	12A956	GASKET, timing cover	1
52	SH604031	SCREW, timing cover to front mounting plate	6
53	LWZ204	WASHER, locking	6
54	PWZ104	WASHER, plain	6
55	SH605061	SCREW, timing cover to mounting plate and block	4
56	LWZ305	WASHER, locking	4
57	PWZ105	WASHER, plain	4

Timing Cover 1974-96 ('simplex' chain with tensioner pad)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
58	12G2623	COVER, front, timing, with oil separator	1	1974-80; includes oil seal.
59	CAM4868	COVER, front, timing, with oil separator	1	1980-91; carburetter models (A Plus type). Includes oil seal.
	LJR10168	COVER, front, timing, with oil separator	1	1991-96 (SPi models 1991-96 and carburetter models 1992-94). Includes oil seal.
60	88G561	OIL SEAL, timing cover	1	Included in 12G2623 and CAM4868 timing covers.
	LUF10006	OIL SEAL, timing cover	1	Included in LJR10168 timing cover.
61	GUG705550GM	GASKET, timing cover	1
62	SH604031	SCREW, timing cover to front mounting plate	6
63	LWZ204	WASHER, locking	6
64	PWZ104	WASHER, plain	6
65	SH605061	SCREW, timing cover to mounting plate and block	5
66	LWZ305	WASHER, locking	5
67	PWZ105	WASHER, plain	5
68	FNZ105	NUT, timing cover to mounting plate	1

Timing Cover 1997 On ('simplex' chain with tensioner pad)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
69	LJR103470	COVER, front, timing, with oil separator	1	1997 on; includes oil seal.
70	LUF10006	OIL SEAL, timing cover	1	Included in timing cover.
71	GUG705550GM	GASKET, timing cover	1
72	ADU6863	SCREW, timing cover to front mounting plate	6
73	ADU6864	WASHER, locking	6
74	ADU8159	SCREW, timing cover to block or front plate	5

Oil System Components
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
75	2K4994	PLUG, priming	1	1969-80; not A Plus cylinder block.
76	6K464	WASHER, sealing	1	1969-80; not A Plus cylinder block.
77	12H865	PLUNGER, oil pressure relief valve	1	Standard fitment.
78	BLS916	BALL, oil pressure relief valve	1	Alternative; see note below.
The ball above may be used in place of the standard fitment plunger to guard against a sticking relief valve (something that the plunger is prone to do, given dirt or metal particles in the oil). It must, however, be used in conjunction with the shorter and stronger AEA536 spring.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
79	6K853	SPRING, oil pressure relief valve	1	Standard fitment.
	AEA536	SPRING, oil pressure relief valve	1	Uprated fitment.
80	12A1851	CAP, threaded, relief valve	1
81	6K431	WASHER, sealing	1
82	2A797	HOUSING, oil pressure relief valve	1	Press-fit in cylinder block.
83	12A1263	DIPSTICK, oil level	1	1969-93, manual gearbox.
	LQM100380	DIPSTICK, oil level	1	1993-96, manual gearbox.
84	12A1262	WASHER, sealing dipstick	1	1969-96, manual gearbox.
85	12A1261	TUBE, dipstick, metal	1	1969-80; manual gearbox. Not A Plus cylinder block.
86	LQM100630	DIPSTICK, oil level	1	1997 on, manual gearbox.
For the dipstick on Minis with automatic gearboxes, please see the 'Automatic Transmission - Torque Converter and Housing' section in the Transmissions area of the Somerford Mini catalogue.

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External Engine - 1275 (not cooper s)

USE: 12G107

HOUSING-DISTRIBUTOR '65 ON-PRE A+

USE: FS106167

WASHER-FIBRE-5/8'' INTERNAL DIAMETER

BLANKING PLUG- 5/58'' UNF -TEMP. SENDER,SERVO,PCV VALVE, ETC

SET SCREW- 1/4'' UNF x 3/8''

SET SCREW- 5/16 UNC x 3/4''

'O' RING-CAMSHAFT SENSOR AND BLANKING PLUG

PLUG-BLANKING-CAMSHAFT SENSOR APERTURE-'97>JAPAN

USE: LWZ205

SET SCREW-5/16'' UNF x 3/4''

WASHER-INTERNAL STAR-1/4'' INTERNAL DIAMETER

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