Somerford Mini Ltd. Ordering Parts Using This Catalogue

Internal Engine - 1275cc (Not Cooper S)
No. Part No. Description Qty. Remarks No. Part No. Description Qty. Remarks
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 a vailable 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
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 1 Set of 4, standard size.
type
21251020 PISTON SET, replacement metric 3 ring 1 Set of 4, +0.020" oversize.
type
21251030 PISTON SET, replacement metric 3 ring 1 Set of 4, +0.030" oversize.
type
21251040 PISTON SET, replacement metric 3 ring 1 Set of 4, +0.040" oversize.
type
21251060 PISTON SET, replacement metric 3 ring 1 Set of 4, +0.060" oversize.
type
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 1 4 piston set, standard size.
pistons
R35960020 RING SET, for replacement metric 3 ring 1 4 piston set, +0.020" oversize.
pistons
R35960030 RING SET, for replacement metric 3 ring 1 4 piston set, +0.030" oversize.
pistons
R35960040 RING SET, for replacement metric 3 ring 1 4 piston set, +0.040" oversize.
pistons
R35960060 RING SET, for replacement metric 3 ring 1 4 piston set, +0.060" oversize.
pistons
1990 On (A Plus)
10:1 Compression Ratio
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 1 4 piston set, standard size.
pistons
BHM1628020 RING SET, for original metric 3 ring 1 4 piston set, +0.020" oversize.
pistons
BHM1628030 RING SET, for original metric 3 ring 1 4 piston set, +0.030" oversize.
pistons
BHM1628040 RING SET, for original metric 3 ring 1 4 piston set, +0.040" oversize.
pistons
BHM1628060 RING SET, for original metric 3 ring 1 4 piston set, +0.060" oversize.
pistons
1992 On (A Plus)
9.4:1 Compression Ratio
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 1 4 piston set, standard size.
pistons
BHM1628020 RING SET, for original metric 3 ring 1 4 piston set, +0.020" oversize .
pistons
BHM1628030 RING SET, for original metric 3 ring 1 4 piston set, +0.030" oversize .
pistons
BHM1628040 RING SET, for original metric 3 ring 1 4 piston set, +0.040" oversize .
pistons
BHM1628060 RING SET, for original metric 3 ring 1 4 piston set, +0.060" oversize .
pistons
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)
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 standard fitment 1275 GT connecting rod is very strong but also ver y heavy. Originally made from
EN19, its material specification was downgraded to EN16 in 1974, at the same time as several other
changes occurred in the engine (when the Duplex timing chain was replaced by a Simplex tensioned chain).
Unfortunately there are no distinguishing features between the EN19 and EN16 items and the same
forging number and part number were used for both, although it’s a fair assumption that if you come
across new ones today they are likely to be made from EN16.
The 1300 GT/Innocenti rod design is lighter than, but as strong as, the standard rod to be found in 1275
GT engines. Made from EN19 material,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 always historically speaking ver y 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.
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)
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 1 Set of 4 pairs, standard size.
8G2553010 BEARING SET, connecting rod, big end 1 Set of 4 pairs, 0.010" undersize.
8G2553020 BEARING SET, connecting rod, big end 1 Set of 4 pairs, 0.020" undersize.
8G2553030 BEARING SET, connecting rod, big end 1 Set of 4 pairs, 0.030" undersize.
8G2553040 BEARING SET, connecting rod, big end 1 Set of 4 pairs, 0.040" undersize.
Crankshaft
Crankshafts shown here are either assemblies (including main bearings , connecting rod bearings and thr ust
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-stamped crankshaft forgings have rolled fillet radii between the bearing journals and webs, which
dramatically improve their fatigue resistance over the previous crankshaft design.
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.
17 8G2740 CRANKSHAFT ASS’Y (with early main 1 1275 GT 1969-80. Stamped no.
bearings) 12G1304, 12G1683 or 12G1505.
BHM1243 CRANKSHAFT ASS’Y (with early main 1 Replacement for 1275 GT. Stamped
bearings)
no. CAM6232 (with rolled fillet radii).
BHM1437 CRANKSHAFT ASS’Y (with late main 1 A Plus 1990 on. Stamped no.
bearings)
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).
Tel. 01249 721421 Fax. 01249 721316 www.somerford-mini.co.uk 27