Internal engine - 1275cc (not cooper s)

Pistons, Piston Rings and Cylinder Liners
Note before ordering a piston set or ring set from Somerford Mini: a set of pistons consists of four pistons complete with rings and gudgeon pins; a set of rings consists of sufficient rings for four pistons. Cylinder liners are supplied individually. Various piston upgrades (superior design and manufacture, different capacities and compression ratios) are also available from Somerford Mini, but are only listed in this catalogue in instances where they make a good, complication-free replacement for original specification pistons which are in short supply.

Pistons listed here are those for original 1275cc Mini engines - i.e. the 1275 GT engine built between 1969 and 1980, plus engines fitted from the resumption of 1275cc Mini production in 1990 onwards. If you have a 1980s Austin or MG Metro 1275cc engine in your Mini, the later A Plus pistons shown here may be applicable in some circumstances, but we strongly advise you to contact Somerford Mini quoting your full engine number before placing an order to ensure you receive the right pistons or rings for your engine.

1969-80 (1275 GT)
8.8:1 Compression Ratio
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
1	12G2088STD	PISTON SET, original 4 ring type	1	Set of 4, standard size.
	12G2088020	PISTON SET, original 4 ring type	1	Set of 4, +0.020" oversize.
	12G2088030	PISTON SET, original 4 ring type	1	Set of 4, +0.030" oversize.
	12G2088040	PISTON SET, original 4 ring type	1	Set of 4, +0.040" oversize.
	12G2088060	PISTON SET, original 4 ring type	1	Set of 4, +0.060" oversize.
	21251STD	PISTON SET, replacement metric 3 ring type	1	Set of 4, standard size.
	21251020	PISTON SET, replacement metric 3 ring type	1	Set of 4, +0.020" oversize.
	21251030	PISTON SET, replacement metric 3 ring type	1	Set of 4, +0.030" oversize.
	21251040	PISTON SET, replacement metric 3 ring type	1	Set of 4, +0.040" oversize.
	21251060	PISTON SET, replacement metric 3 ring type	1	Set of 4, +0.060" oversize.
2	BHM1164STD	RING SET, for original 4 ring pistons	1	4 piston set, standard size.
	BHM1164020	RING SET, for original 4 ring pistons	1	4 piston set, +0.020" oversize.
	BHM1164030	RING SET, for original 4 ring pistons	1	4 piston set, +0.030" oversize.
	BHM1164040	RING SET, for original 4 ring pistons	1	4 piston set, +0.040" oversize.
	BHM1164060	RING SET, for original 4 ring pistons	1	4 piston set, +0.060" oversize.
	R35960STD	RING SET, for replacement metric 3 ring pistons	1	4 piston set, standard size.
	R35960020	RING SET, for replacement metric 3 ring pistons	1	4 piston set, +0.020" oversize.
	R35960030	RING SET, for replacement metric 3 ring pistons	1	4 piston set, +0.030" oversize.
	R35960040	RING SET, for replacement metric 3 ring pistons	1	4 piston set, +0.040" oversize.
	R35960060	RING SET, for replacement metric 3 ring pistons	1	4 piston set, +0.060" oversize.

1990 On (A Plus)
10:1 Compression Ratio
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
3	TAM2050STD	PISTON SET, original metric 3 ring type	1	Set of 4, standard size.
	TAM2050020	PISTON SET, original metric 3 ring type	1	Set of 4, +0.020" oversize.
	TAM2050030	PISTON SET, original metric 3 ring type	1	Set of 4, +0.030" oversize.
	TAM2050040	PISTON SET, original metric 3 ring type	1	Set of 4, +0.040" oversize.
	TAM2050060	PISTON SET, original metric 3 ring type	1	Set of 4, +0.060" oversize.
4	BHM1628STD	RING SET, for original metric 3 ring pistons	1	4 piston set, standard size.
	BHM1628020	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.020" oversize.
	BHM1628030	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.030" oversize.
	BHM1628040	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.040" oversize.
	BHM1628060	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.060" oversize.

1992 On (A Plus)
9.4:1 Compression Ratio
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
5	TAM2048STD	PISTON SET, original metric 3 ring type	1	Set of 4, standard size.
	TAM2048020	PISTON SET, original metric 3 ring type	1	Set of 4, +0.020" oversize.
	TAM2048030	PISTON SET, original metric 3 ring type	1	Set of 4, +0.030" oversize.
	TAM2048040	PISTON SET, original metric 3 ring type	1	Set of 4, +0.040" oversize.
	TAM2048060	PISTON SET, original metric 3 ring type	1	Set of 4, +0.060" oversize.
6	BHM1628STD	RING SET, for original metric 3 ring pistons	1	4 piston set, standard size.
	BHM1628020	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.020" oversize.
	BHM1628030	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.030" oversize.
	BHM1628040	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.040" oversize.
	BHM1628060	RING SET, for original metric 3 ring pistons	1	4 piston set, +0.060" oversize.
7	12G1049	PIN, gudgeon	4	Included in piston sets.
8	AEG428	LINER, cylinder	4	Standard size.

Connecting Rods and Crankshaft
Connecting Rods 1969-80 (1275 GT)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
9	BHM1136	ROD SET, connecting, set of 4	1	Standard fitment.
10	12G1506	ROD ASS'Y, connecting	4	Standard fitment; included in connecting rod set.
	12G1297	ROD ASS'Y, connecting	4	Alternative Austin 1300 GT/Innocenti item.
The 1300 GT/Innocenti rod design is lighter than, but as strong as, the standard rod to be found in 1275 GT engines. It can be easily recognised by its forging number 12G1298 and a small strengthening web across the rod between its flutes (just above the forging number). Ideal for inclusion in a tuned engine, this rod was historically speaking very popular. Somerford Mini still has a limited number in stock, but hurry - when they're gone, they're gone. When changing to a different design of connecting rod, it is of course imperative that all rods are changed at the same time.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
11	LFH10006	BOLT, connecting rod cap ('big end')	8	Included in connecting rod assembly.
12	13H5872	NUT, connecting rod cap ('big end')	8	Included in connecting rod assembly.

Connecting Rods 1990 On (A Plus)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
13	BHM1137	ROD SET, connecting, set of 4	1
14	LFH10006	BOLT, connecting rod cap ('big end')	8	Included in connecting rod assembly.
15	CAM6263	NUT, connecting rod cap ('big end')	8	Included in connecting rod assembly.
16	8G2553STD	BEARING SET, connecting rod ('big end bearings')	1	Set of 4 pairs, standard size.
	8G2553010	BEARING SET, connecting rod ('big end bearings')	1	Set of 4 pairs, 0.010" undersize.
	8G2553020	BEARING SET, connecting rod ('big end bearings')	1	Set of 4 pairs, 0.020" undersize.
	8G2553030	BEARING SET, connecting rod ('big end bearings')	1	Set of 4 pairs, 0.030" undersize.
	8G2553040	BEARING SET, connecting rod ('big end bearings')	1	Set of 4 pairs, 0.040" undersize.

Crankshaft
Crankshafts shown here are either assemblies (including main bearings, connecting rod bearings and thrust washers), or bare (without bearings or thrust washers). However, please note that new crankshafts may be supplied complete with bearings but other times not, depending on what is available at the time. Additionally Somerford Mini can offer a crankshaft regrinding service, usually carried out on your old unit. You should enquire on the current status of supply before ordering a crankshaft from Somerford Mini. The CAM6232 crankshaft, by the way, has rolled fillet radii on the bearing journals which vastly improve its fatigue life.

For details of the primary gear and its bushes located on the tail of the crankshaft, please see the 'Manual Gearbox - Primary, Idler and Drive Gears' section or the 'Automatic Transmission - Torque Converter and Housing' section in the Transmissions area of the Somerford Mini catalogue.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
17	8G2740	CRANKSHAFT ASS'Y (with early main bearings)	1	1275 GT 1969-80. Stamped no. 12G1304, 12G1683 or 12G1505.
	BHM1243	CRANKSHAFT ASS'Y (with early main bearings)	1	Replacement for 1275 GT. Stamped no. CAM6232 (with rolled fillet radii).
	BHM1437	CRANKSHAFT ASS'Y (with late main bearings)	1	A Plus 1990 on. Stamped no. CAM6232 (with rolled fillet radii).
18	12G1505	CRANKSHAFT, bare	1	1275 GT 1969-80. Stamped no. 12G1505.
	CAM6232	CRANKSHAFT, bare	1	A Plus 1990 on; also replacement for 1275 GT. Stamped no.
				CAM6232 (with rolled fillet radii).

There are two distinct main bearing designs: the earlier 8G2391 bearings have locating lugs on the edge of both upper and lower halves, whereas the later BHM1574 bearings have lugs on the edge of the upper halves and in the centre of the lower halves. They cannot be interchanged in engines because the engine main bearing caps are unique for each design. 1275cc engines were not fitted by the factory in Minis during the 1980s; however many owners have chosen to transplant Austin or MG Metro 1275cc engines made in the 1980s into their cars. For the benefit of those owners, the change in main bearing design on the Metro power unit occurred in 1983.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
19	8G2391STD	BEARING SET, main bearings, set of 3 pairs	1	1275 GT 1969-80; std. size.
	8G2391010	BEARING SET, main bearings, set of 3 pairs	1	1275 GT 1969-80; 0.010" undersize.
	8G2391020	BEARING SET, main bearings, set of 3 pairs	1	1275 GT 1969-80; 0.020" undersize.
	8G2391030	BEARING SET, main bearings, set of 3 pairs	1	1275 GT 1969-80; 0.030" undersize.
	8G2391040	BEARING SET, main bearings, set of 3 pairs	1	1275 GT 1969-80; 0.040" undersize.
	BHM1574STD	BEARING SET, main bearings, set of 3 pairs	1	A Plus 1990 on; std. size.
	BHM1574010	BEARING SET, main bearings, set of 3 pairs	1	A Plus 1990 on; 0.010" undersize.
	BHM1574020	BEARING SET, main bearings, set of 3 pairs	1	A Plus 1990 on; 0.020" undersize.
	BHM1574030	BEARING SET, main bearings, set of 3 pairs	1	A Plus 1990 on; 0.030" undersize.
	BHM1574040	BEARING SET, main bearings, set of 3 pairs	1	A Plus 1990 on; 0.040" undersize.

Thrust washers are supplied as a pair; i.e. one upper and one lower thrust washer. Two pairs are required per engine, fitted selectively to obtain the correct amount of end float on the crankshaft.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
20	BHM1293STD	THRUST WASHERS, crankshaft, pair	A/R	Standard size.
	BHM1293003	THRUST WASHERS, crankshaft, pair	A/R	+0.003" oversize.
	BHM1293005	THRUST WASHERS, crankshaft, pair	A/R	+0.005" oversize.
	BHM1293030	THRUST WASHERS, crankshaft, pair	A/R	+0.030" oversize.
21	6K836	KEY, Woodruff, crankshaft	1
22	12G1699	GEAR, timing chain, crankshaft	1	1275 GT 1969-74; for duplex chain.
23	8G725	GEAR, timing chain, crankshaft	1	1275 GT 1974-80; A Plus 1990 on.
				For simplex chain.
Once again, the change dates listed above apply to original Mini engines. For the sake of Mini owners with 1275cc Metro engines in their cars, all Metro engines have simplex timing chains.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
24	6K628	WASHER, packing	A/R
25	12A1148	OIL THROWER, crankshaft	1
26	88G561	OIL SEAL, timing cover	1	Included in timing cover assembly.

Crankshaft Pulley 1969-96
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
27	88G305	PULLEY, crankshaft, with damper	1	1275 GT 1969-76.
	CAM4929	PULLEY, crankshaft, with damper	1	1275 GT 1976-80; can be used to replace 88G305.
	AHU1878	PULLEY, crankshaft, with damper	1	1275 GT 1980; A Plus 1990-96. With timing plate.
28	12A283	BOLT, pulley to crankshaft	1	1275 GT 1969-80.
	TAM2019	BOLT, pulley to crankshaft	1	A Plus 1990-96.
29	12A398	LOCK TAB, pulley bolt	1	1275 GT 1969-80.
	TAM2020	LOCK TAB, pulley bolt	1	A Plus 1990-96.
For Mini owners with 1980s Metro 1275cc engines in their cars, all Metro engines use the AHU1878 pulley, TAM2019 bolt and TAM2020 lock tab.

Crankshaft Pulley 1997 On
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
30	LHF100130	PULLEY, crankshaft, with damper	1	Polyvee belt type.
31	TAM2019	BOLT, pulley to crankshaft	1
32	TAM2020	LOCK TAB, pulley bolt	1

Camshaft and Tappets
A range of uprated camshafts and other engine tuning components are also available from Somerford Mini, but are not listed here. Please contact us for details.

Camshaft 1969-80 (1275 GT)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
33	AEG523	CAMSHAFT, for 'star drive' oil pump	1	1969-80.
	12G2983	CAMSHAFT, for 'slot drive' oil pump	1	1980; A Plus type.

Camshaft 1990 On (A Plus)
For owners with transplanted 1275cc Metro engines in their Minis, please contact Somerford Mini, quoting your full engine number, to ensure you receive the correct camshaft for your engine.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
	CAM6648	CAMSHAFT, for 'slot drive' oil pump	1	10:1 compression ratio carburetter engines.
	LGC10230	CAMSHAFT, for 'slot drive' oil pump	1	10:1 compression ratio single point injection engines.
	LGC105380	CAMSHAFT, for 'slot drive' oil pump	1	10:1 compression ratio multi point injection engines.
	LGC10231	CAMSHAFT, for 'slot drive' oil pump	1	9.4:1 compression ratio carburetter and single point injection engines.
34	CHM108	FLANGE, for 'star drive' oil pump (flange also known as 'spider')	1	Use with 'star drive' type camshaft.
35	12G4499	SPINDLE, distributor drive, centred slot	1	1969-80.
	12G3560	SPINDLE, distributor drive, offset slot	1	1980-96, A Plus type.
36	2A13	TAPPET (also known as cam follower)	8	1969-96; standard size.
	2A13010	TAPPET (also known as cam follower)	8	1969-96; +0.010" oversize.
	LGR100440	TAPPET (also known as cam follower)	8	1997 on; standard size.
37	AEG314	PUSH ROD	8

Timing Chain
Duplex Timing Chain 1969-74
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
38	2H4905	CHAIN, timing, duplex (double row)	1
39	12G1397	GEAR, duplex timing chain, camshaft	1
40	WKN505	KEY, Woodruff	1
41	6K629	NUT, gear to camshaft	1
42	2A759	LOCK TAB, nut	1

Simplex Timing Chain 1974 On
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
43	3H2127	CHAIN, timing, simplex (single row)	1
44	12G4337	GEAR, timing chain, camshaft	1
45	12G2621	PAD, timing chain tensioner	1
46	12G2629	PIN, tensioner pivot	1
47	12G2628	PLATE, tensioner mounting	1
48	SH605061	SCREW, plate to cylinder block	2
49	LWZ305	WASHER, locking	2
50	PWZ105	WASHER, plain	2
51	WKN505	KEY, Woodruff	1
52	6K629	NUT, gear to camshaft	1
53	2A759	LOCK TAB, nut	1

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Internal engine - 1275cc (not cooper s)

CAMSHAFT-1275cc 9.4:1 CR CARB. & SPI ENGINES

CAMSHAFT-1275 A+ 10:1 CR SPI ENGINES

BOLT-CON ROD END CAP-1275cc (NOT 'S')

FLANGE-DRIVING-STAR DRIVE OIL PUMPS

CAMSHAFT-1275 A+ 10:1 CR CARB. ENGINES '90 ON

USE: 13H5872

CRANKSHAFT-BARE 1275cc A+ '90 ON

USE: AHU1878

RING SET-FOR ORIGINAL 3 RING PISTONS 1275cc '90 ON STD. SIZE

RING SET-FOR ORIGINAL 3 RING PISTONS 1275cc '90 ON +060''

RING SET-FOR ORIGINAL 3 RING PISTONS 1275cc '90 ON +040''

RING SET-FOR ORIGINAL 3 RING PISTON 1275cc '90 ON +030''

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