External Engine - 998 and 1098cc

998 and 1098cc Engine Identification
The 998cc A Series engine first saw Mini use in the Riley Elf and Wolseley Hornet Mk II models, introduced in early 1963. By the end of 1963 they had been joined by the 998cc Mini Cooper, which replaced the 997cc Cooper after a short production overlap. 1967 saw the first use of a 998cc engine in a 'standard' Mini, the Mini Mk II 1000. This model, in both manual and automatic gearbox versions and a wide range of trim levels and names, continued in production right the way through to 1992. As with the 848cc engine, 998cc engines used with automatic gearboxes are different in several respects to those used with manual. The Mini Clubman and Clubman Estate shared the Mini 1000's power unit until 1975, after which date the manual Clubmans received the 1098cc A Series (automatics continued with 998cc, there being no automatic type 1098cc engine). When in 1980 the Clubman saloon was dropped, the Estate continued for a further two years, rebadged 'HL' and reverting to 998cc in manual versions.

For 1981 the 998cc A Series engine was relaunched in A Plus specification, in readiness for what was envisaged as a new and prosperous life in the Austin Metro (the Mini wasn't expected to last much longer by then!). The A Plus engine is most easily identified by the reinforcement ribs on the engine block casting; these ribs are missing on the much smoother casting of the pre-A Plus unit. However, just to confuse the issue, the A Plus components were actually introduced gradually between 1979 and 1981, which means that many 'hybrid' engines were built at that time. The Metro, overseas-built Mini Mokes and the very short-lived Allegro 3 are the only BMC/Leyland/Austin Rover vehicles to share the use of the 998cc engine with the Mini.

The 1098cc engine appeared in home market Minis for the first time in the aforementioned Clubman in 1975. The only other UK-built Mini to receive the engine was the Special (1100) of 1979, a limited edition celebrating the 20th anniversary of Mini production. The Special was heavily based on a similar Mini produced for several years in Belgium for mainland European markets, which also used the same engine. Through the 1970s and early 1980s Europe consistently made far more use of the 1098cc A Series in Minis than was the case in the UK.

In common with the 848 and 998cc A Series engines, the 1098cc unit received a pad type timing chain tensioner for 1979, with the tell-tale bulge on the timing cover. Not being destined for use in the forthcoming Austin Metro, the 1098cc engine was not scheduled for the full 1981 A Plus improvement scheme; certain A Plus parts still had to be used from the start of the 1980s however because they were shared with 998cc engine production. The most obvious - and biggest - example of this was the adoption of the A Plus ribbed cylinder block. The best known of other 1098cc A Series applications was without doubt the best-selling BMC ADO16 range (Austin/Morris 1100, MG 1100, etc.). It is very possible if your Mini has received a 1098cc upgrade that the engine started life in one of these cars, especially one of the very nice twin carburetter versions. The only other transverse applications of the engine were overseas-built Mokes (again) and more basic trim level Austin Allegros. Non-transverse applications were legion (Morris Minor, MG Midget, etc.) but are of no consequence here: the engines cannot be adapted to sit on a Mini gearbox.

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 998 and 1098cc engine number prefixes used on 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 relates to the compression ratio of the engine: H for high compression, L for low compression. A Plus high or low compression engines are by contrast identified by the letter plus two digits 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.

998cc Wolseley and Riley Engine Serial Number Prefix Codes 1963-67
9WR/	Manual gearbox (direct change) engines (1963-64)
9AD/	Manual gearbox (remote change) engines without closed circuit breathing (1964-67)
9AE/	Manual gearbox (remote change) engines with closed circuit breathing (1964-67)
9AG/	Automatic gearbox engines without closed circuit breathing (1966-67)
9AJ/	Automatic gearbox engines with closed circuit breathing (1966-67)

998cc Cooper Engine Serial Number Prefix Codes 1963-69
9FA/SA	Manual gearbox (3 Synchro) engine without closed circuit breathing (1963-64)
9FD/SA	Manual gearbox (3 Synchro) engine with closed circuit breathing (1964-68)
9FD/XE	Manual gearbox (4 Synchro) engine with closed circuit breathing (1968-69)
99H/377CH	Manual gearbox (4 Synchro) engine with closed circuit breathing and dynamo (1969)
99H/378CH	Manual gearbox (4 Synchro) engine with closed circuit breathing and alternator (1969)

998cc Wolseley and Riley Engine Serial Number Prefix Codes 1967-69
998cc Austin and Morris Engine Serial Number Prefix Codes 1967-69
998cc Mini Engine Serial Number Prefix Codes 1969-92
1098cc Mini Engine Serial Number Prefix Codes 1975-81
99H/	998cc engines (1967-92)
10H/	1098cc engines (1975-81)
With the advent of 99H/ and 10H/ serial numbers, the codes became far more complex. 99H/ or 10H/ was followed by a three character code, either three digits (issued from 1967-81), or a letter and two digits (1982 onwards). There were not many variations in the Mini 1098cc engine and most have an engine number beginning 10H/791. Engines with A Plus features started to appear around 10H/791/180000, and the A Plus block was in use by 10H/791/217000. Unfortunately there are too many combinations of 99H/ codes to list in the space available here, but if you contact Somerford Mini with your full engine number we can 'unpick' the codes to tell you exactly what specification your engine was built to. We can however give you two important developments later in the life of the 998cc engine denoted by the codes, which mostly ran chronologically in numerical (and from 1982 alpha-numerical) order:
99H/791/431856 Introduction of A Plus cylinder block (plus some engine numbers intermittently for a short period beforehand; 1980-90)
99H/997 Earliest code denoting complete A Plus specification engine (introduced 1980/81)

Additionally, it is helpful to know which A Plus 998cc engines are high (10.3:1) or low (8.3:1) compression ratio, and which are lead-free engines:
High Compression Ratio: 99H/997, 998, A53, A94, A98, B81, B82, C20, D80, D82
Low Compression Ratio: 99H/A19, A97, A99, B83, B84, B85, D83
Lead-Free High Compression Ratio: 99H/D81, E20, E21, F15, F16, F32, G30, G32, G33, G34, G39
Lead-Free Low Compression Ratio: 99H/960, A99, E22, G31

BMC/Leyland/Unipart/Rover Mini 998cc Manual (not Cooper) Reconditioned Engine Part Numbers
8G31	998cc Wolseley and Riley manual gearbox engine (1963-67; replaced by 8G51)
8G47	998cc Wolseley and Riley manual gearbox engine (1963-67; replaced by 8G51)
8G51	998cc Wolseley and Riley manual gearbox engine (1963-67)
8G56	998cc Austin, Morris, Wolseley and Riley manual gearbox engine (1967-69)
8G57	998cc Austin, Morris, Wolseley and Riley manual gearbox engine (1967-80)
GSE1102	998cc manual gearbox engine; later 'Gold Seal' part number. Specification as 8G57 (1967-80)
RKM1102	998cc manual gearbox engine; later 'Silver Seal' part number. Specification as 8G57 (1967-80)
RKM1119	998cc manual gearbox engine; later 'Silver Seal' part number. Specification as 8G57; replaced RKM1102 (1967-80)
8G63	998cc manual gearbox engine, Canada (1972-75)
BHM1061	998cc manual gearbox engine, Canada, Sweden and Japan (1975-80)
BHM1232	998cc A Plus manual gearbox engine, low compression (1980-85)
BHM1377	998cc A Plus manual gearbox engine, high compression (1980-85)
BHM1233	998cc A Plus manual gearbox engine, Japan (1980-85)
BHM1458	998cc A Plus manual gearbox engine, low compression (1985 on)
BHM1460	998cc A Plus manual gearbox engine, high compression (1985 on)
LBB10175	998cc A Plus manual gearbox engine, low compression, lead free (1988 on)
LBB10089	998cc A Plus manual gearbox engine, high compression, lead free (1988 on)

BMC/Leyland/Unipart Mini 998cc Manual (Cooper) Reconditioned Engine Part Numbers
8G33	998cc high compression, without closed circuit breathing, 12G206 cylinder head casting (1963)
8G34	998cc low compression, without closed circuit breathing, 12G206 cylinder head casting (1963)
8G40	998cc high compression, without closed circuit breathing, 12G295 cylinder head casting (1964)
8G39	998cc low compression, without closed circuit breathing, 12G295 cylinder head casting (1964)
8G42	998cc high compression, with closed circuit breathing, 12G295 cylinder head casting (1964)
8G43	998cc low compression, with closed circuit breathing, 12G295 cylinder head casting (1964)
8G49	998cc high compression, with closed circuit breathing, 12G295 cylinder head casting, warning light type oil filter head (1964-69)
8G48	998cc low compression, with closed circuit breathing, 12G295 cylinder head casting, warning light type oil filter head (1964-69)
GSE1103	998cc high compression engine; later 'Gold Seal' part number. Specification approximately as 8G49 (1964-69)
RKM1103	998cc high compression engine; later 'Silver Seal' part number. Specification approximately as 8G49 (1964-69)
RKM1120	998cc high compression engine; later 'Silver Seal' part number. Specification approximately as 8G49; replaced RKM1103 (1964-69)

BMC/Leyland/Unipart/Rover Mini 998cc Automatic Reconditioned Engine Part Numbers
8G58	998cc Austin, Morris, Wolseley and Riley automatic gearbox engine (1967-69)
8G59	998cc Austin, Morris, Wolseley and Riley automatic gearbox engine (1967-80)
BHM1041	998cc Austin and Morris automatic gearbox engine (1974-80)
BHM1235	998cc A Plus automatic gearbox engine, low compression (1980-85)
BHM1378	998cc A Plus automatic gearbox engine, high compression (1980-85)
BHM1461	998cc A Plus automatic gearbox engine, high compression (1985 on)
LBB10088	998cc A Plus automatic gearbox engine, high compression, lead free (1985 on)
LBB10176	998cc A Plus automatic gearbox engine, low compression, lead free (1985 on)

BMC/Leyland/Unipart Mini 1098cc Reconditioned Engine Part Numbers
BHM1042	1098cc manual gearbox engine, 'Gold Seal' (1975-80)
RKM1150	1098cc manual gearbox engine, 'Silver Seal' (1975-80)
BHM1229	1098cc manual gearbox engine with A Plus cylinder block, 'Gold Seal' (1980-81)
RKM1151	1098cc manual gearbox engine with A Plus cylinder block, 'Silver Seal' (1980-81)

Note that where no differentiation is made between open circuit or closed circuit breathing, or between dynamo or alternator fitment, the factory instructed that the parts concerned (rocker cover, tappet cover, pulley etc.) should be swapped over from the old engine to the new one as required.

Rebuilt or Repaired 998 and 1098cc 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.
	GEG254	GASKET SET, conversion ('bottom end set')	1	1967-79, automatic gearbox models.
	LVQ10035	GASKET SET, conversion ('bottom end set')	1	1979 on, automatic gearbox models.
Conversion gasket sets (often called 'bottom end' or 'supplementary' sets) include gaskets for the following: water pump, front cover, tappet chest covers, 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, tappet chest covers, distributor housing and oil suction pipe. Note that the tappet chest cover gaskets included are the post-1966 rubber type - customers requiring the earlier cork gaskets should purchase them separately.
	EGS001	GASKET SET, full engine	1	Manual gearbox models.
The 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	2K8169	PLUG, core (welch), cylinder block, 1 5/8" dia.	4	1963-80.
	AEC876	PLUG, core (welch), cylinder block, 1 3/8" dia.	4	1980 on (A Plus block).
3	2K1345	PLUG, oil pressure release valve passage	2	1963-85.
	TAM2009	PLUG, oil pressure release valve passage	2	1985 on.
4	12H1734	PLUG, oil gallery, solid brass	2	1963-85, 998cc.
	CAM4133	PLUG, oil gallery, cup type	2	1985 on, 998cc.
	12G3503	PLUG, oil gallery	2	1098cc.
5	ADP210	PLUG, oil feed	1	Automatic gearbox.
6	1B3664	WASHER, sealing	1	Automatic gearbox.
7	1A1964	RESTRICTOR, cam bearing oil feed	1
8	CAM150	STUD, cylinder head, long	4
9	CAM151	STUD, cylinder head, short	5
10	CHS2513	STUD, fuel pump drive aperture	2	1963-69.
	CHS2515	STUD, fuel pump drive aperture	2	1969 on.
From 1963-69 the fuel pump drive aperture studs secured a blanking plate, plus the open circuit breathing vent pipe (if fitted). From 1969 onwards, they secured the mechanical fuel pump. For mechanical fuel pump fixing details, including the gasket (which is not the same as the blanking plate gasket), please see the 'Fuel Pumps - Carburetter' section in the Fuel and Exhaust Systems area of the Somerford Mini Catalogue.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
11	2A265	PLATE, blanking fuel pump drive aperture	1	1963-69.
12	GUG705557GM	GASKET, blanking plate	1	1963-69.
13	FNZ105	NUT, blanking plate to block	2	1963-69.
14	LWZ205	WASHER, locking	2	1963-69.
15	PWZ105	WASHER, plain	1	Required for open circuit breathing vent pipe bracket (if fitted).
16	53K615	STUD, oil filter head	2	Manual gearbox, 1963-73. For paper element oil filters.
	CHS2613	STUD, oil filter head	2	Manual gearbox, 1973 on. For 'spin on' cartridge oil filters.
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	12A1910	SCREW, main bearing cap to block	6
22	2A54	DOWEL, main bearing cap	6
23	6K927	LOCK TAB, main bearing cap screw	6
24	BHM1211	LINER SET, camshaft bearings	1
25	3H576	TAP, cooling system drain	1	Alternative to plug; fitted up to early 1980s.
26	2K4954B	WASHER, fibre, drain tap	A/R
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
27	53K2853	PLUG, cooling system drain	1	Alternative to tap; fitted throughout production.
28	6K638B	WASHER, sealing plug	1
29	2A612	HOUSING, distributor	1	1963-65; does not require O ring.
30	12A1136	HOUSING, distributor	1	1965 on; requires O ring.
31	13H2792	O RING, housing	1	1965 on.
The later 12A1136 distributor housing may be fitted in place of the earlier 2A612 housing, but only if a 13H2792 O ring is fitted with it.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
32	SH604061	SCREW, housing to block	2	1963-80; not A Plus cylinder block.
33	LWZ404	WASHER, shakeproof	2	1963-80; not A Plus cylinder block.

Engine Front Mounting Plate
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
34	2A970	PLATE, engine front mounting	1	1963-79.
35	12G2626	PLATE, engine front mounting	1	1979 on. Accepts chain tensioner.
36	12G619B	GASKET, plate to block	1	1963-79.
	GUG705554GM	GASKET, plate to block	1	1979 on. Accepts chain tensioner.
37	SH605051	SCREW, plate to block	2
38	LWZ305	WASHER, locking	2
39	53K2016	SCREW, plate to main bearing cap	2
40	6K831	LOCK TAB, screw	1	1963-69.
41	WF600041	WASHER, shakeproof	2	1969 on. Will replace lock tab on earlier engines.
42	AHU2379	PLATE, camshaft locating	1
43	SH604061	SCREW, plate to block	3
44	WF600040	WASHER, shakeproof	3

Timing Cover 1963-79 (without chain tensioner pad)
Several timing covers were fitted in the 1960s, some with timing pointers, some without, most with stiffeners, one without. All were superseded by 1970 by 12G2506, which includes a timing pointer and lower stiffener and does not require the stiffener 12A666 listed below. The plain washers PWZ104 and PWZ105 listed below replace the original elongated washers used at different times on the A Series engine until the 1980s.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
45	12G2506	COVER, front, timing	1	Includes oil seal.
46	88G561	OIL SEAL, timing cover	1	Included in timing cover.
47	12A666	STIFFENER, timing cover	1	Use on early 1960s covers suffering from poor sealing.
48	12A956	GASKET, timing cover	1
49	SH604031	SCREW, timing cover to front mounting plate	6
50	LWZ204	WASHER, locking	6
51	PWZ104	WASHER, plain	6/3	Qty. reduced when stiffener is present.
52	SH605061	SCREW, timing cover to mounting plate and block	4
53	LWZ305	WASHER, locking	4
54	PWZ105	WASHER, plain	4/3	Qty. reduced when stiffener is present.

Timing Cover 1979 On (with chain tensioner pad)
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
55	CAM4641	COVER, front, timing, accepts chain tensioner pad	1	1979-80; includes oil seal.
	CAM4904	COVER, front, timing, accepts chain tensioner pad	1	1980 on; includes oil seal. A Plus type.
56	88G561	OIL SEAL, timing cover	1	Included in timing cover.
57	GUG705550GM	GASKET, timing cover	1
58	SH604031	SCREW, timing cover to front mounting plate	6
59	LWZ204	WASHER, locking	6
60	PWZ104	WASHER, plain	6
61	SH605061	SCREW, timing cover to mounting plate and block	5
62	LWZ305	WASHER, locking	5
63	PWZ105	WASHER, plain	5
64	FNZ105	NUT, timing cover to mounting plate	1

Tappet Chest Covers
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
65	-	COVER, tappet chest, LH, with breather pipe	1	Convex cover; for open circuit breathing (1963-66).
66	-	COVER, tappet chest, LH, with breather pipe	1	Concave cover; for open circuit breathing (1966-69).
67	12G577	COVER, tappet chest, LH, with oil separator	1	Convex cover; for closed circuit breathing (1964-66).
68	12A1212	COVER, tappet chest, LH, with oil separator	1	Concave cover; for closed circuit breathing (1966 on).
There are too many varieties of LH tappet chest cover for open circuit engine breathing models to list here. However they are all detailed, along with all of the other components of each type of breathing system, in the 'Emission Controls - Engine Breathing' sections in the Fuel and Exhaust Systems area of the Somerford Mini catalogue.

Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
69	12H941	COVER, tappet chest, RH	1	Convex cover, 1963-66.
70	12A1386	COVER, tappet chest, RH	1	Concave cover, 1966 on.
71	12A1139	GASKET, cover, cork	1	For convex type cover.
72	BH605151	BOLT, cover to block	1	For convex type cover.
73	2K4958	WASHER, bolt	1	For convex type cover.
74	GUG705505GM	GASKET, cover, rubber	1	For concave type cover.
75	SH605091	SCREW, cover to block	1	For concave type cover.
76	12A1177	WASHER, cup	1	For concave type cover; 1963-85.
77	12A1176	BUSH, rubber	1	For concave type cover; 1963-85.
78	MRC1980A	BUSH, rubber	1	For concave type cover; 1985 on.
The MRC1980A bush is commonly fitted in place of the 12A1177 washer and 12A1176 bush on pre-1985 engines.

Oil System Components
Ill. No.	Part No.	Description	Qty. Rqd.	Remarks
79	2K4994	PLUG, priming	1
80	6K464	WASHER, sealing	1
81	12H865	PLUNGER, oil pressure relief valve	1	Standard fitment.
82	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
83	6K853	SPRING, oil pressure relief valve	1	Not 998cc Cooper.
	AEA536	SPRING, oil pressure relief valve	1	998cc Cooper.
84	12A1851	CAP, threaded, relief valve	1
85	6K431	WASHER, sealing	1
86	2A797	HOUSING, oil pressure relief valve	1	Press-fit in cylinder block.
87	12A116	DIPSTICK, oil level	1	1963-66; manual gearbox.
	12A1263	DIPSTICK, oil level	1	1966 on; manual gearbox.
88	AEC671	WASHER, sealing dipstick	1	1963-66; manual gearbox.
	12A1262	WASHER, sealing dipstick	1	1966 on; manual gearbox.
89	12G107	TUBE, dipstick, nylon	1	1963-66; manual gearbox.
	12A1261	TUBE, dipstick, metal	1	1966-80; manual gearbox. Not A Plus engines (see note below).
Note that 'hybrid' engines (with A Plus cylinder block, but not all other A Plus features) produced in the 1979-81 period also did not require a dipstick tube. 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 - 998 and 1098cc

BALL-OIL PRESSURE RELIEF VALVE-ALTERNATIVE FITMENT

CAMSHAFT BEARING SET-997,998,1098 AND 1275 AUTO.

BOLT-5/16'' UNF x 1 7/8''

PLATE-CAMSHAFT LOCATING

PLUG-CORE-1 5/16'' DIAMETER, A+ and 1275cc

SEAL- DIPSTICK A SERIES/AUTOMATIC-'65-'85

SPRING-OIL PRESSURE RELIEF-UPRATED FITMENT & COOPER '61-'71

OIL SEAL-TIMING CHAIN COVER '59-'90

GASKET-OIL FILTER HEAD- '59-'73 & AUTO. FILTER ADAPTOR

LOCK TAB-MAINS CAP-NOT 1275cc

SPRING-OIL PRESSURE RELIEF-STANDARD FITMENT

USE: LWZ404 x 2

We accept