Back to

Technical Data

Technical Data
for the MG Y Series - YA and YT

ENGINE:

Type:      XPAG/SC2. Four cylinders, water cooled, with overhead valves, push-rod operated, with detachable head.

Bore

66.5 mm (2.62 in.).

Stroke

90 mm (3.54 in.).

Capacity

1250 c.c. - (76.28 cu. in.).

Bore/stroke ratio

1.353 to 1

Compression ratio

7.2/7.4.

Depth of head

45.5 c.c.

  Cylinder head gasket

  0.045 in (1.14mm.) thick copper and asbestos

RAC Rating

10.97 hp.

CONNECTING ROD:

Type

Steel

  Length

  178 mm with loose steel shell white-metal bearings.

  Bore at big-end

  48.658 mm — 48.671 mm

  Bore at small end

  18 mm.    +.03 mm
  —.01 mm

  Width at big-end

  27.865 mm — 27.890 mm

  Width at small end

  19 mm

  Gudgeon pin

Type: Clamp. Dia.: 18 mm. - .015mm.  Length 58.5mm.

       - .010mm.

CRANKSHAFT:

  Diameter

Width

  Radius

Main journal (front)

52 mm     — .035 mm.
  — .015 mm.

38 mm.

2.5 mm.±.15 mm

Intermediate journal

52 mm     — .035 mm.
  — .015 mm.

38 mm     — .02 mm.
  — .01 mm.

2.5 mm.±.15 mm

Main journal (rear)

52 mm     — .035 mm.
  — .015 mm.

40 mm.

2.5 mm.±.15 mm

Crankpin journal

45 mm     — .035 mm.
  — .015 mm.

28 mm     — .015 mm.
  — .010 mm.

2.5 mm.±.15 mm

Minimum regrind

43.75 mm.

MAIN BEARINGS:

Bore size of crankcase for main bearings

56.34 mm. ± .02mm.

Diameter

Width

Main bearing (front)

52.020 mm
52.005 mm

35.12 mm.
34.88 mm.

Main bearing (inter.)

52.020 mm
52.005 mm

37.955 mm.
37.925 mm.

Radius 2.75 mm.
U/cut .25 mm.

Main bearing (rear)

52.020 mm
52.005 mm

35.12 mm.
34.88 mm.

Main bearing clearance on crankshaft diameter

.020 mm
.055 mm.

Main bearing (inter.) end-float on crankshaft

.035 mm.
.095 mm.

BIG-END BEARING:

Diameter

Width

Thickness

45 mm.

22.46 mm.
22.21 mm.

1.825 mm.
1.831 mm

Big-end clearance on crankshaft diameter

.011 mm.
.056 mm.

 CRANKSHAFT REGRIND
 

Bearing and crankshaft dia. undersize

Reference

Crankshaft main journal std. and regrind sizes

Crankpin journal std. and regrind sizes

Main bearings std. and regrind sizes

Standard

Standard

52 mm.

45 mm.

52.020 mm
52.005 mm

.5 mm
(.020 in.)

R.2

51.5 mm.

44.5 mm.

51.520 mm.
51.505 mm.

1.00 mm.
(.040 in.)

R.4

51.00 mm.

44.00 mm.

51.020 mm.
51.005 mm.

  CAMSHAFT DRIVING CHAIN:

  Renold chain number 114036 (duplex)
     Type: Roller ³⁄₈ in. pitch. 60       pitches endless.

  CAMSHAFT BEARINGS:

Front Bearing: White metal.  Outside diameter 43.61 mm. Press fit in cylinder block. Inside diameter to be reamed in position in cylinder block to 41 mm.+.05 mm/+.08 mm.

  Centre and rear bearings: Zinc alloy

  Outside diameter 43.5 mm.+.00 mm.
       — .02 mm.
Inside diameter 23 mm.      +.015 mm.
       — .005 mm.

  Bore of cylinder block for bearings

  43.5 mm. +.02 mm.
  — .01 mm.

  CAMSHAFT:

End-float: .005 in. — .013 in. (.125 mm. — .325 mm.).

  Diameter of shaft for bearing:

  Front: 41 mm.   +.01 mm.
   — .02 mm.
Centre and rear: 23 mm.   +.05 mm.
     — .08 mm.

  Cam lift

  5.334 mm. = 8 mm. at valve.

Cam Timing

5 - 45 - 45 - 5

  VALVES AND GUIDES

  Valve port throat diameter

  Inlet: 30 mm.
Exhaust: 26 mm.

  Valve head diameter

  Inlet: 33 mm.
Exhaust: 31 mm.

  Valve stem diameter

  8 mm.±.01 mm.

  Valve seat angle

  30˚.

  Valve guides

  Bore: 8.06/8.08 mm.
Outside diameter: 14 mm.    +.02 mm.
        +.04 mm.

  Valve guide length

  Inlet: 59 mm.
Exhaust: 54 mm.

Valve spring pressure

Inner

Outer

Shut

31 lb. (14.1 kg)

62 lb (28.1 kg)

Open

43 lb (19.5 kg)

82 lb (37.2 kg)

Valve lift

8.0 mm.

Valve timing

Commencing Engine No. XPAG/SC/16831

Exhaust opens

45˚ B.B.D.C.

Exhaust shuts

5˚ A.T.D.C.

Inlet opens

5˚ B.T.D.C.

Inlet shuts

45˚ A.B.D.C.

Valve clearance (early models)

.019 in. (.48 mm.). (engine hot)

Valve clearance (commencing Engine No. XPAG/SC2/18097)

.012 in. (.30 mm.). (engine hot)

LUBRICATION:

Oil pump speed

Half engine speed, gear type.

Oil pressure

70 lb./sq. in. to 40 lb./sq. in.
(5.0 kg./cm.² to 2.8 kg./cm.²).

Oil pump by-pass

60 lb./sq. in. (4.2 kg./cm.²).

Oil sump capacity

9 Pints (5.1 litres).

Oil sump capacity (commencing Engine No. XPAG/SC2/17383)

10.5 Pints (6.0 litres).

Oil filter

Full-flow type.

IGNITION:

Ignition timing

T.D.C.

Order of firing

1, 3, 4, 2.

Sparking plugs

Champion L.10.S. 14 mm. (Champion
NAB on later models)

Sparking plug gap

.020 in. to .022 in. (.51 mm. to .56 mm.).

Contact Breaker Gap

.014 - .016 in. (.36 mm. - .40 mm.)

PISTONS:

Type: Aluminium alloy, tin coated, controlled expansion.

Width

Diameter

Compression ring groove

.0886 in. (2.250 mm.)
.0087 in. (2.253 mm.)

2.381 in. (60.477 mm.).
2.385 in. (60.579 mm.).

Oil control ring groove

.1576 in. (4.003 mm.)
.1577 in. (4.006 mm.)

2.389 in. (60.680 mm.).
2.393 in. (60.782 mm.).

Side clearance of rings in grooves

.001 in. (.025 mm.).
.002 in. (.050 mm.).

Width

Radial thickness

2 off. Compression rings

.0885 in. (2.248 mm)

.109 in. (2.768 mm.).
.101 in (2.565 mm.).

1 off Slotted oil control ring (8 slot)

.1575 in. ( 4.0 mm.)

.105 in. (2.667 mm.).
.097 in. (2.464 mm.).

Piston ring gap

.006 in. to .010 in.
(.15 mm. to .25 mm.).

Gudgeon pin bore

18 mm.     — .0001 in (.0025 mm.).
  — .0003 in. (.0076 mm.).

Cylinder bore oversize in thousandths of an inch

Cylinder bore size in mm.

Cylinder bore size in inches

Piston size reference

Standard

66.50

2.6181

A...OK

19.7

67.00

2.6378

C...OK

39.4

67.5

2.6575

E...OK

Piston size
(across thrust faces below oil rings)

Piston marking

Suitable fore bore size

in.

mm.

in.

mm.

2.6156
2.6160

(66.436)
(66.446)

To suit "STD" bore

2.6181
2.6185

(66.500)
(66.510)

2.6161
2.6165

(66.449)
(66.459)

To suit +.0005 bore

2.6186
2.6190

(66.513)
(66.523)

2.6166
2.6170

(66.462)
(66.472)

To suit +0010 bore

2.6191
2.6195

(66.525)
(66.535)

2.6171
2.6175

(66.474)
(66.484)

To suit +0015 bore

2.6196
2.6200

(66.538)
(66.548)

Piston size
(across thrust faces below oil rings)

Piston marking

Suitable fore bore size

in.

mm.

in.

mm.

2.6356
2.6360

(66.944)
(66.954)

To suit +0200 bore

2.6381
2.6385

(67.008)
(67.018)

2.6361
2.6365

(66.957)
(66.967)

To suit +.0205 bore

2.6386
2.6390

(67.021)
(67.031)

2.6366
2.6370

(66.970)
(66.980)

To suit +0210 bore

2.6391
2.6395

(67.033)
(67.043)

2.6371
2.6375

(66.982)
(66.992)

To suit +0215 bore

2.6396
2.6400

(67.046)
(67.056)

Piston size
(across thrust faces below oil rings)

Piston marking

Suitable fore bore size

in.

mm.

in.

mm.

2.6556
2.6560

(67.453)
(67.463)

To suit +0400 bore

2.6581
2.6585

(67.516)
(67.526)

2.6561
2.6565

(67.465)
(67.475)

To suit +.0405 bore

2.6586
2.6590

(67.529)
(67.539)

2.6566
2.6570

(67.478)
(67.488)

To suit +0410 bore

2.6591
2.6595

(67.541)
(67.551)

2.6571
2.6575

(67.490)
(67.500)

To suit +0415 bore

2.6596
2.6600

(67.554)
(67.564)

PROPELLER SHAFT:

Type

Hardy Spicer needle bearing (balanced).

Length

Face to face 45 ⁵/₁₆ in. (1.151 m.).

Tubular shaft

2½ in. diameter (6.35 cm.).

Joint size

KR—1111. GB 22/1118—GB 65.

CLUTCH:

Type

Single dry plate—Borg & Beck

Diameter

8 in. (20.3 cm.).

Facings

RYZ

Thrust springs

150 to 160 lb./in.
(26.8 to 28.6 kg./cm.).
Colour "Brown"

Clutch plate damper springs

6 off (Black/Green)

GEARBOX:

Four speed, synchromesh second, third, and fourth gears

Oil capacity

1¼ pints (0.7 litre)

Gearbox ratios

Overall ratios

Top

1 to 1

5.143 to 1

Third

1.385 to 1

7.121 to 1

Second

2.07 to 1

10.646 to 1

First

3.50 to 1

18.000 to 1

Reverse

350 to 1

18.000 to 1

INSTRUMENTS:

Speedometer

British Jaeger Model 58597.  Type SC.52

Reduction gear for speedometer

6/15 ratio

HYDRAULIC DAMPERS:

Girling piston type front and rear

Type: Front
   Rear

Luvax Girling PVA6X.
Luvax Girling PVA6.

COOLING SYSTEM:

Cooling by radiator, pump and fan with thermostat control

Total capacity of system

13½ pints (7.7 litres).

Capacity of radiator

7½ pints (4.3 litres).

Circulation

By pump fitted in front of cylinder block.

Drain taps

1. Bottom of radiator
1. Front end of cylinder block below exhaust manifold

FUEL SYSTEM:

Fuel tank capacity (level checked by electric gauge on instrument panel)

8 gals. (36 litres)

Fuel delivery

S.U. electric pump.  12-volt. Type "L".

Carburetter

Type H.2 Spec. 456.

Carburretter needles

Standard  Richer      Weaker
  "F.I."        "D.K."      "E.F."

STEERING:

Rack and pinion

2.625 turns from lock to lock.

Steering wheel

Adjustable for length 3 in. (76.2 mm.).

FRONT AXLE:

Camber of wheel

1˚ Neg. ±1˚.

Castor angle

1˚ ±½˚.

King-pin angle

10˚.

Toe-in

Nil.

Knuckle angle

10˚.

WIRE DIA.(GROUND)

.538"

MEAN COIL DIA.

3.238"

RATE

435 LB/INCH

No OF EFFECTIVE COILS

7.34

FREE LENGTH

9.82" ± ¹/₁₆"

TO CARRY 1023 LB. AT:-

7.47" ± ¹/₃₂"

TO CARRY 1390 LB AT:-

6.63" ± ¹/₃₂"

SOLID HEIGHT

5.025

REAR AXLE:

Type

Semi floating.

Crown wheel and pinion

Hypoid.

Oil capacity

2¾ pints (1.3 litre).

Axle tooth ratio

5.125 to 1 (⁸/₄₁).

Crown wheel and pinion backlash

By spacers and special tools.

No OF LEAVES

7 x ¼" x ½"

WORKING LOAD

650 LBS

STATIC DEFLECTION

3"

MEAN RATE

216.6 LBS/INS

FREE CAMBER

4"

MAX. DEFLECTION

6¼"

WHEELS:

Type

Dunlop No. CDM.317 Ventilated disc.

Wheel size

4J X 15.

Tyre size

5.50–15.

Tyre pressures

Front: 22 lb. per sq. in. (1.5 kg./cm.²).
Rear: 24 lb. per sq. in. (1.68 kg./cm.²).

BRAKES:

Type

Lockheed hydraulic.  Hand brake cable to rear only.

Linings

Ferodo M.R.19.

Brake-drums

9 in. diameter +.005 in./ - .000 in.
(22.9cm. diameter +.127mm./ - .000mm.).

Length of lining

8¾ in. (22.22 cm.).

Width

1½ in. (3.81 cm.).

Thickness

³⁄₁₆ in. (4.76 mm.).

Number per car

8.

Rivets

Hollow countersunk head (brass).

Number of rivets per lining

12.

GENERAL DIMENSIONS:

Wheelbase

8 ft. 3 in. (2.515 m.).

Track:     Front
   Rear

3 ft 11 ³⁄₈ in. (1.203 m.).
4 ft. 2 in. (1.270 m.).

Overall length

13 ft. 8 in. (4.165 m.).

Overall width

4 ft. 10 ¼ in. (1.480 m.).

Overall height

4 ft. 9 in. (1.448 m.).

Ground clearance

6 in. (15.2 cm.).

Turning circle

33 ft. (10.21 m.). L/H and R/H lock.

WEIGHTS:

Complete car

20 cwt. 3 qr. (1054 kg.).

Front

10 cwt. (506 kg.).

Rear

10 cwt. 3 qtr (508 kg.).

Chassis

10 cwt. 2 qr. 22 lb (543 kg.).
Bumpers fitted, less wings and lamps.

Power unit (with gearbox)

3 cwt. 2qr. 5lb. (180 kg.).

PERFORMANCE:

Brake horse-power

46 b.h.p. at 4,800 r.p.m.

Maximum torque

702 lb. in. (8.1 kg.). at 2,400 r.p.m.

Litres per ton-mile

2480.-Top gear.

M.p.h per 1,000 r.p.m.

14.5.  Top gear.

K.p.h. per 1,000 r.p.m.

23.33.  Top gear.

Engine speed per 10 m.p.h.

689 r.p.m.  Top gear.

*Petrol consumption

36.5 m.p.g. at 30 m.p.h.
(13 km. per litre at 48 k.p.h.)
32.7 m.p.g. at 40 m.p.h.
(11.5 km. per litre at 64 k.p.h.)
29.0 m.p.g. at 50 m.p.h.
(10.3 km. per litre at 80 k.p.h.)

*ACCELERATION:

0—30 m.p.h. (0—40 k.p.h.) in 7.5 seconds
0—50 m.p.h. (0—80 k.p.h.) in 18.8 seconds
0—60 m.p.h. (0—100 k.p.h.) in 29.5 seconds

Brake horse-power per litre capacity

36.8.

Maximum speed

69 m.p.h. (100 k.p.h.) average.

*BRAKING.  DRY CONCRETE:

30 m.p.h. (48.2 k.p.h.) 31 feet (9.45 m.).
50 m.p.h. (80.4 k.p.h.) 92 feet (28.04 m.).
70 m.p.h. (112.6 k.p.h.) 227 feet (69.19 m.).

Hand brake braking. Dry tarmac. 30 m.p.h. (48.2 k.p.h.) 45 feet (13.7 m.).

* Extracts from Motoring Press

ELECTRICAL:

12-volt ignition and equipment; coil ignition controlled by automatic advance and retard mechanism, incorporated in the distributor.  Dynamo output controlled by automatic compensated voltage control unit.

Starter type

Lucas Model M.35.G1

Starter switch

Lucas Model ST.18.  Type L/15.

Distributor type

Lucas Model DKYH.4A. (Part No. 40089).
       Later models are Part No. 40058F.
       Rotation - anti clock.

Dynamo*

Lucas Model CP.39.PV2.

Dynamo speed

1.16 engine speed.

Coil type

Lucas Model Q12—8. Type L/O.

Control unit*

Lucas Model RF.95/2.  Type L/2, 12 volt.

Battery

Lucas 12-volt, 51-amp.-Type GTXW.9A.

Windscreen wiper

Lucas Model CR.2.DA.36.

*It is important that control box Lucas Model RF.95/2 is used in conjunction with the Lucas Model CP.39 type dynamos

LAMPS:

Headlamps

Lucas Model MBD.140.

Sidelamps

Lucas Model 1130.

Fog-lamp

Lucas Model FT.57. Type L/1.

Stop and tail-lamp

Lucas Model ST.50.

Reverse and tail-lamp

Lucas Model RT.50

Back to

Technical Data