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Policy
Last updated:
01 September 2010
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Technical Data and Specifications Whilst every attempt has been made to ensure the data is correct, the authors
of this site cannot be held responsible for the information. Specific information is also given in the
Austin Motor Co. handbook for each model. Much more detail can be found in
'The Austin Seven Source Book' by Bryan Purves. Pub: Haynes Publishing,
Sparkford, Yeovil, Somerset. ISBN 0 85429 557 7.
If any 'Seven' enthusiast
feels that the data should be corrected, or extended, please contact
CA7C
Engine Data;
Gearbox Data;
Transmission Data; Chassis and Suspension Data;
Electrical Data: Austin Seven
Threads
Engine specification
Bore 2.2" (55.88 mm)
Stroke 3" (76.2 mm)
Capacity - standard 747.5 cc
Compression Ratio (up to mid 1936) 4.8 : 1
Compression Ratio (post mid 1936) 6 : 1
b.h.p. 1922 10 @ 2400 rpm
b.h.p. 1923 - 1932 10.5 @ 2400 rpm Sports 24 @ 5000 rpm (1930-32)
b.h.p. 1933 - 1934 12 @ 2600 rpm Sports 21 @ 4400 rpm
b.h.p. 1935 13.5 @ 3000 rpm Sports 23 @ 4800 rpm
b.h.p. 1936 16.5 @ 3400 rpm Sports 23 @ 4800 rpm
b.h.p. 1937 17 @ 3800 rpm Sports 23 @ 4800 rpm
Timing
Pre 1935 1 7/8" B T D C (20 degrees)
Mk1 Ruby engine 3/4" B T D C at flywheel P oints
should be just opening.
Firing Order 1 3 4 2
Contact breaker points 1929 - 1931 0.020" CAV electrics
Contact breaker points 1932 - 1936 0.014" Lucas electrics
Contact breaker points 1936 - 1939 0.012" Lucas electrics
Champion No 7 Sparking Plugs 1922 - 1936 Low compression engine
Champion L10 Sparking Plugs 1936 - 1939 High compression engine
Sparking plug gap 0.018" to 0.020"
Valve clearances
Inlet - standard engine 0.004" Hot 0.006" Cold
Exhaust - standard engine 0.004 Hot 0.007" to 0.008" Cold
Inlet - sports engine 0.004" to 0.006" Hot 0.008" Cold
Exhaust - sports engine 0.006" to 0.008" Hot 0.010" Cold
Big
End Bearings
- Standard engine not pressure fed
Big end clearance to crank pin 0.001" to 0.002" Optimum clearance
Crank pin out of round 0.003" P referred
maximum
Big end nuts torque around 20 ft. lbs.
Small End Bolts
Small end bolts
Bolt Heads should face off-side of engine
Camshaft
End float 0.002"
Lubrication
Normal Oil Pressure - 2 bearing crank up to 5 p.s.i.
Normal Oil pressure - 3 bearing crank up to 5 p.s.i.
Oil filter Gauze in sump C lean
every 4000 - 5000 miles
Oil grade S.A.E. 30 or equivalent (avoid detergent oils)
in an engine that has not been totally cleaned.
Sump capacity standard engine 4 pints
Sump capacity sports engine 8 pints
Cooling System
Capacity 9½ pints approx
Pistons & Rings
Split skirt piston
Split on nearside of engine
Piston to cylinder clearance 0.0015" Split skirt piston
Piston to cylinder clearance 0.004" Plain skirt piston
Ring Gap 0.003" to 0.006"
Lubrication
Oil grade - standard S.A.E. 40 E ngine
oil.
Oil grade - sports S.A.E. 50
Oil capacity 1922 - 1932 2/3 pint
Oil capacity 1933 - 1939 1½ pints
Rear Axle
Oil grade - standard 140 grade
Oil capacity 7/8 pint
Front Springs
1924-1925 5 leaves 30" bush centres
1926-1929 5 leaves 29 1/4" bush centres
1929-1934 8 leaves 29 1/4" bush centres
Rear Springs
1924-1925 6 leaves 23 1/4" hole to bush centres
1926-1934 7 leaves 23 1/8" hole to bush centres
Dynamo
1922 - 1928 C.A.V. dynamo Output approximately 5 to 6 amps
1928 Lucas Short dynamo
1929 - 1932 Lucas Longer dynamo
1931 - 1935 Lucas C35A Brushes
without leads
1935 - 1939 Lucas C35M Brushes with leads
Distributors
Sept 1928 ? Both Lucas
and and alternative fitted
late 1931 Lucas DJ4 manual
advance
July 1934 - 1936 Lucas DK4A Auto Advance 3 degrees
July 1936 - 1939 Lucas DK4A Auto Advance 8 degrees
The following information has been obtained from a 1932 LWB
Box Saloon, variations may have been used by Austin during the production
history of the Seven.
Size
Type
TPI
Use
1/4
BSF
26
General Bolts and Setscrews. Engine/ Manifold Studs.
5/16
BSF
22
General Bolts and Setscrews. Engine/ Cylinder Head and Gearbox Studs.
Shock Absorber Link Bolts
3/8
BSF
20
Bolts and Setscrews . Wheel Studs. Shock Absorber Link Bolts. Dynamo
Spindle Com End. Springs "U" Bolts.
7/16
BSF
18
Dynamo Spindle/Castle Nut. Front Brake Shoe Pivot Pin.
1/2
BSF
16
Steering Swivel Axle/Cross Tube Levers. Brake Pedal Fulcrum Pin. Rear
Spring Through Bolts.
1/4
BSW
20
Oil Sump Bolts.
5/16
BSW
18
Studs Crankcase/Bell-housing. Oversize Sump Bolts.
3/8
BSW
16
Studs Bell-housing (Stepped Oversize).
2
BA
31.4
Fittings. Door Hinges Mounting ("A" Post).
3/4
SPECIAL
14
Drain Plugs Gearbox/ Engine/Back Axle and Gearbox Filler Plug.
3/4
BSC ?
20
Steering Cross Tube and Jaws. Plug Top of King Pins.
5/8
SPECIAL
16
Axle Shafts / Radius Arms/Crankshaft (front)
7/8
SPECIAL
12
Crankshaft (rear)
1–1/4
SPECIAL
16
Rear Hub Bearing Retaining Nut. Torque Tube Socket. Screw Cores Engine
Block.
1–3/8
SPECIAL
16
Hubs.
3/4
BSC/BSB
26
Gearbox Speedometer Drive Bush and Cable Ends.
3/8
BSC
26
Front and Rear Shock Absorbers Centre Bolt.
7/16
BSC
26
Headlamp Mounting Bolts/Nuts.
1/2
BSC
26
Starter Motor Spindle/Nut. Replacement Front Shock Absorber Centre
Bolts.
1/8
BSP
28
Shackle Repair. Grease Plug Hole-Hubs. Grease Nipples Fitting Holes.
1/4
BSP
19
Pipe/Fittings. Brake Rope Guides. Rear Axle Filler Plug. Rear Axle
Breather Pipe. Petrol Pipes Unions.
3/8
BSP
19
Speedometer Drive Bush Gearbox.
These abbreviations have been used.
BA = British Association
BSP = British Standard Pipe
BSB = British Standard Brass
BSW = British Standard Whitworth
BSC = British Standard Cycle
SPECIAL = Whitworth Form Special
BSF = British Standard Fine
TPI = Threads Per Inch
Further information on:
BA, BSW and BSF Drilling and Tapping Data
http://dspace.dial.pipex.com/town/lane/xvo73/eng/eng_data.htm produced
by Guy Weatherall.
This information was collated by Malcolm Watts, Peter Kemp and others,
whilst rebuilding their Austin Sevens.
