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Austin Healey Sprite - M. G. Midget
"A"-SERIES ENGINE DETAILS
Dimensions are in inches unless otherwise stated.
(information from SPRITE, MIDGET, 1958-71
AUTOBOOK, by Kenneth Ball, Autopress Ltd. 1971) |
| Bore
and Stroke (mm): |
| |
948 cc |
62.94 X 76.20 |
| |
1098 cc |
64.58 X 83.72 |
| |
1275 cc |
70.61 X 81.28 |
|
Compression ratio (low): |
| |
948 cc
('Sprite' I and II, 'Midget' I) |
8.3:1 |
| |
1098 cc
('Sprite' II and III, 'Midget' I and II) |
8.1:1 |
| |
1275 cc
('Sprite' IV, 'Midget' III) |
8.0:1 |
|
Compression ratio (high): |
| |
948 cc
('Sprite' I and II, 'Midget' I) |
9.0:1 |
| |
1098 cc
('Sprite' II and III, 'Midget' I and II) |
8.9:1 |
| |
1275 cc
('Sprite' IV, 'Midget' III) |
8.8:1 |
| Firing
Order |
1-3-4-2 |
| Main
bearings, journal diameter: |
| |
All
capacities except 'Sprite III and IV, 'Midget' II and III |
1.7505-1.7510 |
| |
1098 cc
and 1275 cc ('Sprite' III and IV, 'Midget' II and III) |
2.0005-2.0010 |
| Main
bearing liners, running clearance |
| |
948 cc
('Sprites' and 'Midgets') |
.001 to .0025 |
| |
1098 cc
('Sprites' and 'Midgets') |
.001 to .0025 |
| |
1275 cc
('Sprite' IV, 'Midget' III) |
.001 to .0027 |
| Main
Bearings, lining material |
| |
'Sprite'
I |
Whitemetal |
| |
948 cc
('Sprite' II and 'Midget' I) |
Lead/indium |
| |
1098 cc
('Sprites' and 'Midgets') |
Lead/indium |
| |
1275 cc
('Sprite' IV, 'Midget' III) |
VP3 lead/indium or
nfm/3B |
|
Crankshaft regrind undersizes |
| |
948 cc
and 1098 cc |
-.010, -.020, -.030,
-.040 |
| |
1275 cc |
No more than >010
without heat treatment |
|
Crankshaft end float (all Capacities) |
.002 to .003 |
| Crankpin
diameter (all capacities) |
1.6254 to 1.6259 |
|
Connecting rod centers (all capacities) |
5.75 |
| Big-end
bearings, running clearance (all capacities) |
.001 to .0025 |
| Big-end
bearings, lining material |
Copper/lead |
| |
948 cc
('Sprite' II and 'Midget' I) |
Lead/indium |
| |
1098 cc
and 1275 cc ('Sprites' and 'Midgets') |
Lead/indium |
|
Connecting rod end float on crankpin (all capacities) |
.008 to .012 |
| Clamped
gudgeon pin: |
| |
Diameter |
.6244 to .6246 |
| |
Clearance in piston |
.0001 to .0003 |
| Fully
floating gudgeon pin (fit in piston -1098cc) |
Hand push |
| Gudgeon
Pin (1275 cc) |
| |
Fit in
small end (interference) |
Pressed in
small-end, .0008 to .0015 |
| |
Fit in
piston |
Hand push |
| Piston
Type |
Aluminum alloy |
|
Standard piston, suitable bore size: |
| |
948 cc |
2.4778 to 2.4781 |
| |
1098 cc |
2.5424 to 2.5447 |
| |
1275 cc |
2.7803 to 2.7800 |
| Piston
oversizes: |
| |
948 cc |
+.010, +.020, +.030,
+.040 |
| |
1098 cc
and 1275 cc |
+.010 and +.020 |
| Piston
clearance, bottom of skirt: |
| |
948 cc
('Sprite' I) |
.0010 to .0016 |
| |
949 cc
('Sprite' II, 'Midget' I ) |
.0016 to .0022 |
| |
1098 cc |
.0005 to .0011 |
| |
1275 cc |
.0015 to .0021 |
| Piston
clearance, top of skirt: |
| |
949 cc
('Sprite' II, 'Midget' I ) |
.0036 to .0042 |
| |
1098 cc |
.0021 to .0037 |
| |
1275 cc |
.0029 to .0037 |
| Piston
rings, compression: |
| |
Top |
Plain |
| |
Second |
Taper |
| |
Third |
Taper |
| Fourth
piston ring, all capacities except 1275 cc and later 1098cc |
Slotted scraper |
| |
1275 cc
and later 1098 cc |
Duraflex 61 |
| Width
of compression rings: |
| |
948 cc |
.0690 to .0700 |
| |
1098 cc
(top ring) |
.0620 to .0625 |
| |
1098 cc
(second and third rings), 1275 cc (all three) |
.0615 to .0625 |
| Width
of slotted scraper ring: |
| |
All
capacities except 1275 cc and later 1098 cc |
.124 to .125 |
| Ring
gap, fitted, all capacities except 1275 cc |
.007 to .012 |
| |
1275 cc
(top ring) |
.011 to .016 |
| |
1275 cc
(second and third rings) |
.008 to .013 |
| |
Duraflex
61 (rails and side spring) |
.012 to .028 |
| Ring
clearance in groove |
| |
948 cc,
1275 cc (top, second and third) |
.0015 to .0035 |
| |
1098 cc |
.0020 to .0040 |
|
Camshaft journal diameters: |
| |
Front |
1.6655 to 1.666 |
| |
Center |
1.62275 to 1.62325 |
| |
Rear |
1.3725 to 1.3735 |
|
Camshaft bearings: |
| |
Front |
Steel-backed
whitemetal |
| |
Center
and rear ('Sprite' I) |
Direct in crankcase |
| |
(All
'Sprites' and 'Midgets', except 'Sprite' I, have three whitemetalled bearing
liners) |
|
Camshaft clearance: |
| |
Front
bearing (also center and rear when linered) |
.001 to .002 |
| |
Center
and rear bearings |
.00125 to .00275 |
| Camshaft
end float |
.003 to .007 |
| Timing
chain |
Single roller
(Duplex on 1275 cc) |
| timing
chain, pitch |
.375 |
| Timing
chain, length |
52 pitches |
| Valve
seat angle |
45 deg. |
| Valve
lift: |
| |
948 cc
('Sprite' I) |
.285 |
| |
949 cc
('Sprite' II, 'Midget' I ) |
.312 |
| |
1098 cc |
.312 |
| |
1275 cc |
.318 |
| Valve
head diameter, inlet: |
| |
948 cc
('Sprite' I) |
1.0937 |
| |
949 cc
('Sprite' II, 'Midget' I ) |
1.151 to 1.156 |
| |
1098 cc |
1.151 to 1.157 |
| |
1275 cc |
1.307 to 1.312 |
| Valve
head diameter, exhaust |
| |
948 cc
('Sprites' and 'Midgets') |
1.00 to 1.005 |
| |
1098 cc |
1.00 to 1.005 |
| |
1275 cc |
1.1515 to 1.1565 |
| Valve
stem diameter, inlet: |
| |
948 cc
('Sprites' and 'Midgets') |
.2793 to .2798 |
| |
1098 cc
and 1275 cc |
.2793 to .2798 |
| Valve
stem diameter, exhaust (all capaciteis) |
.2788 to .2793 |
| Valve
stem clearence, inlet (all capacities) |
.0115 to .0025 |
| Valve
stem clearance, exhaust: |
| |
948 cc
and 1098 cc |
.0020 to .0030 |
| |
1275 cc |
.0015 to .0025 |
| Valve
rocker clearance (cold): |
| |
All
capacities |
0.012 |
| |
Competition work |
0.015 |
|
For checking timing only: |
| |
948 cc
('Sprite' I) |
0.019 |
| |
949 cc
('Sprite' II, 'Midget' I ) |
0.021 |
| |
1098 cc |
0.021 |
| |
1275 cc |
0.029 |
| Valve
springs ---free length |
| |
948 cc
('Sprite' I) |
1.750 |
| |
948 cc
('Sprite' II, 'Midget' I ), inner |
1.672 |
| |
950 cc
('Sprite' II, 'Midget' I ), outer |
1.750 |
| |
1098 cc
('Sprites' and 'Midgets'), inner |
1.672 |
| |
1098 cc
('Sprites' and 'Midgets'), outer |
1.750 |
| |
1275 cc
('Sprite' IV, 'Midget' III), inner |
1.703 |
| |
1275 cc
('Sprite' IV, 'Midget' III), outer |
1.828 |
| Valve
spring pressure (valve closed): |
| |
948 cc
('Sprite' I) |
52.5 lb |
| |
948 cc
('Sprite' II, 'Midget' I ), inner |
18 lb |
| |
950 cc
('Sprite' II, 'Midget' I ), outer |
52 lb |
| |
1098 cc
('Sprites' and 'Midgets'), inner |
18 lb |
| |
1098 cc
('Sprites' and 'Midgets'), outer |
52 lb |
| |
1275 cc
('Sprite' IV, 'Midget' III), inner |
25 lb |
| |
1275 cc
('Sprite' IV, 'Midget' III), outer |
51 lb |
| |
| Valve
timing ('Sprite' I): |
| |
Inlet
opens |
5 deg. Before TDC |
| |
Inlet
closes |
45 deg. After BDC |
| |
Exhaust
opens |
40 deg. Before BDC |
| |
Exhaust
closes |
10 deg. After TDC |
| |
With
rocker clearance of .019, for checking only |
| Valve
timing (948 cc 'Sprite' II and 'Midget' I. All 1098 cc and 1275 cc): |
| |
Inlet
opens |
5 deg. Before TDC |
| |
Inlet
closes |
45 deg. After BDC |
| |
Exhaust
opens |
51 deg. Before BDC |
| |
Exhaust
closes |
21 deg. After TDC |
| |
With
rocker clearance of .021, for checking only (.029 for 1275
cc) |
| Oil sump
capacity including filter (pints) --- all capacities |
6 1/2 |
| |
| Oil
pressure relief valve springs, free length: |
| |
'Sprite'
I |
2 7/8 |
| |
Later
'Sprites' and 'Midgets' |
2.86 |
| |
| Oil
pressure (normal running), lb/sq in: |
| |
All
except 'Sprite' IV and 'Midget' III |
60 |
| |
'Sprite'
IV and 'Midget' III |
40 to 70 |
| |
| Exhaust
emission control |
| |
Exaust
gas analyser reading: |
| |
At engine idling
speed |
2 to 2.5% CO
(provisional) |
| |
Air pump test speed |
1200 rev/min
(engine) |
Sprite Tech Data Index
Austin Healey Sprite - M. G. Midget
SU CARBURETOR DETAILS
Dimensions are in inches unless otherwise stated.
(information from SPRITE, MIDGET, 1958-71
AUTOBOOK, by Kenneth Ball, Autopress Ltd. 1971)
| Type (Sprite I) |
SU H.1 (two) |
| Needle (normal) |
GG |
| Type (Sprite II and Midget I, 948 cc) |
SU H.S.2 (two) |
| Needle (Standard) |
V3 |
| Needle (Rich) |
V2 |
| Needle (Weak) |
GX |
| Spring |
Light Blue |
| Type (1098 cc Sprite II and Midget I) |
SU H.S.2 (two) |
| Needle (Standard) |
GY |
| Needle (Rich) |
GG |
| Needle (Weak) |
M |
| Spring |
Blue |
| Type (1098 cc Sprite III, Midget II, 1275
cc Sprite IV, Midget III |
SU H.S.2 (two) |
| Needle (Standard) |
AN |
| Needle (Rich) |
H6 |
| Needle (Weak) |
GG |
| Spring |
blue |
| Spring (Sprite IV and Midget III) |
Light Blue |
| Fuel pump (all models except Sprite III
and IV and Midget II and III) |
AC 'Y' type (mechanical) |
| Sprite III and IV, Midget II and III |
SU type A.U.F. (Electric) |
| Type (1275 cc Sprite IV, Midget III)
Exhaust emission control |
SU H.S.2 (two) |
| Specification: Exhaust emission control: |
|
| |
Fixed needle type |
AUD 266 |
| |
Spring-loaded type |
AUD 328 |
| Needle, fixed type, exhaust emission
control |
AN |
| |
Spring-loadaed type, exhaust emission control |
AAC |
| Piston spring, exhaust emission control |
Blue |
| Initial jet adjustment, exhausted emission
control |
11 flats from bridge |
| Idling speed, exhaust emission |
1000 rev/min |
| Fast-idle speed, exhaust emission |
1100 to 1200 rev/min |
Sprite Tech Data Index
Austin Healey Sprite - M. G. Midget
IGNITION SYSTEM DETAILS
(information from SPRITE, MIDGET, 1958-71
AUTOBOOK, by Kenneth Ball, Autopress Ltd. 1971)
| Spark plug type all capacities cxcept
Sprite IV and Midget III |
Champion N5 |
| Spark plug type (Sprite IV and Midget III) |
Champion N9Y |
| Spark plug gap |
0.025 |
| Contact breaker gap |
0.014 |
| Static setting, Premium fuel: |
|
| |
948 cc (high compression) Sprite I |
5 deg. before TDC |
| |
948 cc (high compression) Sprite II and Midget I |
4 deg. before TDC |
| |
1098 cc (high copression) Sprite III and Midget II |
5 deg. before TDC |
| |
1275 cc (high comression) Sprite IV and Midget III |
7 deg. before TDC |
| |
1275 cc (Sprite IV and Midget III) Exhaust emission
control |
4 deg. before TDC |
| Static setting (low compression): |
| |
948 cc (Sprite II and Midget I) |
1 deg. before TDC |
| |
1098 cc (Sprite III and Midget II) |
3 to 5 deg. before TDC |
| |
1275 cc (Sprite IV and Midget III) |
7 deg. before TDC |
| Stroboscope setting at 600 engine rev/min: |
| |
1098 cc (Sprite III and Midget II) |
8 deg. before TDC |
| |
1275 cc (Sprite IV and Midget III) at 1200 rev/min |
22 deg. |
| Stroboscope setting at 1000 engine
rev/min: |
| |
1275 cc (Sprite IV and Midget III) Exhaust emission
control |
10 deg. before TDC |
| Distributor type (lucas) |
| |
Sprite I |
D.M.2-P.H.4 |
| |
948 cc Sprite II and Midget I |
D.M.2-P.4 |
| |
1098 cc and later 125 cc |
25 D.4 |
| |
1275 cc (early - no vacuum control) |
23 D.4 |
| Coil type (Lucas): |
| |
All models except Sprtie IV and Midget III |
L.A. 12 |
| |
Sprite IV and Midget III |
11 C.12 |
Sprite Tech Data Index
Austin Healey Sprite - M. G. Midget
CRITICAL NUT & BOLT TORQUES
Dimensions are in lbs/foot unless otherwise stated.
(information from SPRITE, MIDGET, 1958-71
AUTOBOOK, by Kenneth Ball, Autopress Ltd. 1971)
| Cylinder head nuts (except Sprite IV and
Midget III) |
40 |
| Sprite IV and Midget III (studs 22 or
small indent) |
50 |
| Sprite IV and Midget III (plain studs) |
42 |
| Main bearing cap bolts |
60 |
| Big-end cap bolts (except Sprite IV and
Midget III) |
35 |
| Sprite IV and Midget III |
45 |
| Crankshaft pulley nut |
70 |
| Gudgeon pin clamp screw |
25 |
| Flywheel bolts |
35 to 40 |
| Rocker pedestal nuts |
25 |
| Sump to crankcase bolts |
6 |
| Rocker cover bolts |
4 |
| Oil pump securing bolts (Sprite IV and
Midget III) |
12 |
| Oil filter |
10 to 15 |
| Steering column pinch bolt (Sprite IV and
MidgetIII) |
10 |
| Deep-pressed cylinder side cover (Sprites
III and IV, Midgets II and III) |
5 |
| Steering wheel nut |
41 |
| Disc to hub |
40 to 45 |
| Caliper to hub |
45 to 50 |
| |
Steering column - top fixing bolts |
12 to 17 |
| |
|
pinion pinch bolt |
9 to12 |
| |
Steering wheel nut |
37 |
| |
Master cylinder port adaptors |
33 |
| |
Plastic reservoir fixing bolts |
5 |
| |
Pressure failure switch (nylon) |
15 lb in |
| |
Pressure failure switch assembly end plug |
200 lb in |
| Front hub nuts |
25 to 65 |
Sprite Tech Data Index
Austin Healey Sprite - M. G. Midget
GEARBOX DETAILS
(information from SPRITE, MIDGET, 1958-71
AUTOBOOK, by Kenneth Ball, Autopress Ltd. 1971)
| Oil capacity (pints) |
|
|
|
2 1/3 |
|
|
| Gear Raitos (overall) |
|
First |
Second |
Third |
Top |
Reverse |
| |
Sprite I |
15.276 |
10.018 |
5.95 |
4.22 |
19.665 |
| |
948 cc Sprite II and Midget III |
13.504 |
8.085 |
5.726 |
4.22 |
17.361 |
| |
1098 cc and 1275 cc Sprites and Midgets |
13.504 |
8.085 |
5.726 |
4.22 |
17.32 |
| |
Post 1969 models |
12.48 |
7.472 |
5.292 |
3.9 |
16.044 |
| |
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