Engine Series – MG XPAG

T Total: Lotus and the M.G. XPAG engine


The engine series are neither technical treatise or Haynes Manuals. This information is readily available in published form or on the net.

Rather our study concentrates on how and why Chapman and his colleagues’ sourced engines and their contribution to Lotus success and sales.

In his selection of major mechanical components Chapman added both performance to a sophisticated chassis and extraordinary added value.

Lotus were not a major engine manufacturer until quite late on. Despite this they used and adopted a range of mainstream engines to extraordinary effect.

Chapman and Lotus practice provides inspiration for all Industrial Designers /Specialists in their search for urgency and added value.

Our study focuses heavily on the fitment of these engines along with a visual representation. We debate the appeal to owners / racers and the beneficial publicity accredited to the manufacturers.

We believe that subscribers will be well able from this base line to research specific topics according to their needs.

Subscribers might like to see complementary A&R articles including:

Lotus Mk.VIII

  • The 1172 Formula
  • Lotus Mk.VI – several themed
  • Lotus Seven – -do-
  • After Market Suppliers-Aquaplane, Elva ohv conversion etc.
  • S.U. Carburettors-All Choked Up
  • Coventry Climax Engines
  • Austin Powers –Austin Engines
  • Ford 1172 engines
  • Ford Consul engine and pre cross flow , crossflow
  • Cosworth engines
  • Coventry Climax
  • Heads you Win:Laystall-Lucas and Lotus

T Time

The following comparative data helps explain the importance of the MG engine;-

Standard Engine Data

Marque Model Bore Stroke CC Net BHP Rpm C’Ratio Carbs
Austin 7 63 68 848 31.5 5500 8.3 1 Zenith
Austin A35 63 76 948 4750 8.3 1 Zenith
Austin Sprite 63 76 98 42.5 5200 8.3 2 S.U.
Ford Popular 63 92 1172 36 4500 7 1 Solex
Ford Prefect 81 48 997 39 5000 8.9 1 Solex
Ford Consul 82 79 1703 59 4400 7.8 1 Zenith
Hillman Minx 79 76 1494 53 4600 8.5 1 Zenith

Statistics taken from the net:-

XPAG 1250cc MG TB OHV engine 11HP.
XPJM 1140cc Morris 10/4 ohv engine 10HP.
XPJW 1140cc Wolseley 10/40 ohv engine 10HP.
USHM 918cc Morris Minor MM SV engine 8HP.
XPEG 1488cc MG TF OHV engine 13HP.
MPJG 1292cc MG TA engine ohv 12HP.
MPJM 1292cc Morris 12/4 OHV engine 10HP.
MPJW 1292cc Wolseley 12/48 OHV engine 10HP.
APHM 803cc Morris Minor MM OHV engine, 8HP.
APJM 948cc Morris Minor 1000 OHV engine 10HP.
TPBG 1549cc MG VA ohv engine 12HP.
TPDG 1705cc MG ‘Cream Cracker’ TA engine.
QPJG 2322cc MG WA ohv engine 18HP.
QPHW 2561cc Wolseley 18/80 ohv engine 18HP.
XPAG standard engine data XPAW standard engine data
  • Bore: 66.5mm
  • Stroke: 90mm
  • Capacity: 1250cc
  • Firing Order: 1342
  • Spark Plugs: Champion L.10.S
  • Compression Ratio: 7.25:1
  • Valve timing: inlet opens 10 degrees BTDC, closes 57 degrees ABDC. Exhaust opens 52 degrees BBDC, closes 24 degrees ATDC.
  • Valve lift: 8mm inlet & exhaust
  • Tappet clearance: .019 hot
  • Ignition timing: TDC
  • Carburators: Twin 1 1/4″ SU
  • B.M.E.P.: 125@ 2,600 RPM
  • Safe maximum RPM: 5,700
  • Valve crash: 6,000
  • Capacity of combustion space: 45cc
  • Cylinder head thickness: 3.0177
  • Thickness of head gasket: .045
  • Capacity of head gasket: 4.5cc
  • Top Gear overall ratio: 5.125:1
  • MPH / 1,000 RPM: 15.84
  • Tyre size: 4.50×19
  • Octane Rating: Minimum requirements for knock free operation = 74 octane. For maximum power = 82 octane

MG Engine performance comparisons from Robson

Marque MG MG MG
Years 1949-53 1953-54 1955-59
Prod ‘No’s 29,664 6,200 58,750
Engine Nuffield XPAG-type BMC B series
cylinders 4 in-line 4 in line
valves ohv ohv
cc 1,250cc 1,489cc
bore/stroke 66.5x90mm 73.02×88.9mm
bhp 54@5200rpm 57bhp@5500rpm 68-72bhp@5500rpm
gearbox 4 speed 4 speed
max.speed 80mph 100mph
0-60mph 19.4sec 15sec
standing 1/4m 21.3sec 19.3sec
o’all fuel consum’ 30mpg 28mpg
Marque MG
Model TF 1500
Years 1954
Prod ‘No’s
cc 1466cc
bore/stroke 72x90mm
bhp 63bhp@5000rpm
max.speed 85mph
0-60mph 16sec
standing 1/4m 20.5sec
o’all fuel consum’ 30mpg


Figure 1.Image from the net .This handbook would have guided tuners in the 1950’s and its likely Lotus owners with MG engines would have studied.


Figure 2.Exploded parts drawing from the net. The editors believe this image is more revealing than a photograph, where much of the engine is concealed from view. This also helps explain the construction and performance inherent in design.

Brief Tech spec from Buckley and Rees


Engine: In line four

Capacity: 1250-1466cc

Power: 54-63 bhp

Transmission: 4 speed manual

No Built: 10,000 TC. 29,664 TD. 9,800 TF.


Figure 3.Editor’s photograph of i. Lotus Mk.VI fitted with Laystall improved M.G.engine and ii. MG engine in Y type saloon .This might have been the source of MG equipped Lotus cars?.

The MG Y-Type is a small saloon and limited production open four-seat tourer that was built by MG between 1947 and 1953.

When production ceased, 8,336 “Y” Types had been produced, 6,131 of which were “YA”s, 904 were “YT” Tourers and 1,301 were “YB”s.

Engine [edit]

The power unit was a single carburettor version of the 1,250 cc engine used in the latest MG-TB. This engine, the XPAG, went on to power both the MG-TC and MG-TD series. The MG Y Type saloon developed 46  bhp at 4,800 rpm, with 58.5 lb. ft. of torque at 2,400 rpm, the YT Tourer (with the higher lift camshaft and twin carburettors) develop 54 bhp (40 kW). With the exception of only the Rover Ten, which managed 2 additional bhp, the “Y” Type had more power than other British saloons of similar size. Indeed at the time many manufacturers were still producing side valve engines.

MG Gearbox

The Racing Engines Price list produced by Lotus in August 1955 quotes a price of £54 for MG.TC gearbox complete with remote control.


Figure 4.Image from the net. The MG engine was a performance engine that was accentuated by a standard matching complementary 4 speed gearbox that was compact and reasonably light. Significantly it was 4 speed compared with Ford 3 speed unit.


Figure 5.Further image from the net of item advertised as TA gearbox

T for Two

Taylor describing the Lotus Mk.VIII comments:-

“Since Peter Gammon had been enjoying such success with his M.G. powered Mk.VI the M.G.XPAG looked an attractive choice.

Chapmans prototype was built from M.G.and Morris parts, with a Laystall –Lucas light alloy cylinder head and twin SU carburetors and developed around 85 bhp at 6200rpm”

Images of Lotus with MG engines


Morland includes 2 examples of the Lotus Mk.VI with excellent photographs.

Form and Function

Subscribers are invited to examine this sketch in conjunction with existing working drawing of Lotus Mk.VI


Figure 6.Editors sketch drawing of M.G.XPAG engine in front and side elevation

Performance figures [approx.]: taken from Lotus Mk.VI sales brochure

Ford 10 Degree of tuning Normal/Perfect Limits of 1172 Formula Special cam etc.
Maximum speed 75 mph 88 mph 94 mph
Petrol consumption 45 mpg 48 mpg 40 mpg
Standing 1/4 mile 21 secs. 19 secs. 17.5 secs.
Ford Consul Degree of tuning Normal Consul Twin Carbs etc. Special cam etc.
Maximum speed 99 mph 106 mph 113 Plus
Petrol consumption 40 mpg 42.5 mpg 38 mpg
Standing 1/4 mile 18.8 secs. 17.4 secs. 16.5 secs.
M.G Degree of tuning Normal 1250 Max.of 1250 1500 Special cam etc.
Maximum speed 104 mph 113 mph 120 mph
Petrol consumption 40 mpg 42.5 mpg 38 mpg
Standing 1/4 mile 17.8 secs. 16.5 secs. 15.8 secs.

Lotus Mk.VI –MG-Laystall

Laystall tuned engines gave a performance advantage. A dedicated A&R articles outlines their contribution.


Figure 7.Editors sketch of Laystall tuned engine in Lotus Mk.VI

Lotus Mk.VI: UPE 9

The editors attribute considerable credit to this car and the early establishment of the Lotus reputation and mystique. This car and its driver dominated a season and wiped the board often against much more expensive and sophisticated machinery.

Admittedly UPE 9 was possibly built to a very high specification with components and details not incorporated in the more mainstream Ford 1172 cars.

Possibly much of the success of UPE 9 could be attributed to its specially prepared MG engine.

Later Chapman would use the MG engine in the Lotus Mk.VIII

He gave this car an extraordinarily aerodynamic body designed by Costin in order the limitations of a mass-produced engine could be compensated for.

RAC British GP. Silverstone, 17th July, 1954

No. Car Chassis Registry Engine Type Size Cyl. Turbo
1 Buckler
2 Kieft LDA 1 Climax FWA 1100 cc
3 Kieft Climax
4 Lotus Mark VI
5 MG Special MG
6 Morris Minor Riley
7 Osca MT4 1134 MO24307 Osca no:1123 1100 cc L4 N/A
9 Porsche 550 09 Porsche 1100 cc F4 2v DOHC N/A
10 Lotus Mark VIII MG
11 Lotus Mark VIII 8/01 SAR 5 MG 1500 cc L4
12 Lotus Mark VI UPE9 MG 1500 cc L4
13 Lotus Mark VI NUF 100 MG
14 Connaught ALSR 12 MCA 200 Lea Francis 1500 cc L4 N/A
15 Lotus Mark VIII Connaught 1500 cc L4
16 Cooper Disco Volante Connaught 1500 cc L4
17 Cooper T29 MG
18 Gordini T15S 0018S Gordini 1500 cc L4
19 Kieft AJB
20 Killeen K1 K1 MG XPAG 1500 cc L4
21 MG TD Special MG
22 MG MG 1500 cc
23 MG …AH. MG
24 Lister BHL1 MER303 MG 1500 cc
25 Tojeiro MG
27 Leonard MG 1500 cc L4
29 Lester T51 MG 6850 MG
30 Osca MT4 Osca 1350 cc L4 N/A
31 Tojeiro MG
32 Turner
33 Porsche 550 Porsche 1500 cc F4 2v DOHC N/A

Entered cars that did not arrive:

No. Car Chassis Registry Engine Type Size Cyl. Turbo
26 Leonard MG
28 Leonard MG

Learning Opportunities

Our learning /educational opportunities are intended to be challenging thought provoking and requiring additional research and/or analysis.

These opportunities are particularly designed for a museum/education centre location where visitors would be able to enjoy access to all the structured resources available in conjunction with any concurrent exhibition.

In this instance we suggest the following might be appropriate:-

  • Outline MG marque history – what are the origins of the engine?
  • What speed records did MG undertake? How might this have developed the engine?
  • What were the likely donors for the MG powered Lotus in period?
  • What were the advantages of the MG 4 speed gearbox?
  • In addition to MG engine identify other significant specification of UPE 9 that gave it such edge?
  • Was UPE 9 “credible” in terms of performance /race results? What was the contribution of the owner driver?
  • What other manufacturers / marques used Mg engines in specialist brands?
  • Identify other significant Lotus cars that used MG engine, numerically and race results wise / publicity – how important was the contribution?
  • Estimate the cost effectiveness of the MG engine over other alternatives
  • To what extent did Chapman need to give the MG engine an aerodynamic body to compensate and compete against better funded marques?

Exhibitions, Education and Economics

In the museum context the editors believe that commercial considerations are both necessary and complementary with its educational objectives.

For these reasons our suggested outline Business Plan includes provision for promoting products and services which share Chapman’s ideals of mechanical efficiency and sustainability. In addition we propose merchandising that explain and interprets the social and cultural context of Chapman’s designs in period. It’s suggested there will be catalogue for on line purchasing.

In this instance the following are likely to prove both educational and entertaining: –

  • Lotus’s “T” time
  • Suited Lotus down to a T
  • T Total
  • Lotus :Crossing their “T’s”
  • Lotus with a capital “T”


The MG engine powered the Lotus

It therefore powered racing and road cars.

It was a superb piece of industrial design ; functional and utilitarian .

It was successful in racing gaining publicity and inspired modification, tuning and a generation chassis designers.

The engine was attractive to owners and generated sales. Exports were possible because of the international spares availability.

These mass-produced engines were robust, inexpensive, widely available and spawned aftermarket components industry. Furthermore, they invited experimentation, and helped facilitate competition and design diversification. Thus assisting and elevating British motor racing :design , engineering , manufacture and of course drivers.

In the case of the MG it contributed significantly to a generation of sports racing cars and race formula in the early to mid 1950’s. It had considerable appeal in the USA.

The engine has continuing legacy and relevance and being such a significant piece of industrial design is fully worthy of analysis and appreciation.

Added value is an extremely important of Industrial Design, Chapman exploited to maximum effect and its principles are significant for a young entrepreneur’s with low capital wishing to enter the market.


Classic Cars. Buckley and Rees.Southwater.214.

ISBN: 9781780193977

The Cars of BMC.Robson.MRP.1999.

ISBN: 1899870415

The Lotus Book. Taylor .Coterie.

Lotus Seven. Morland.

Please note the editors of the A&R attempt to give the broadest spectrum of references but not all are available for consultation in an article. However by noting their existence it may assist students in their research.

*Items in italics non A&R library books.