Engine specification
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| Bore |
2.2" ( 55.88 mm) |
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| Stroke |
3" ( 76.2 mm ) |
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| Capacity - standard |
747.5 cc |
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| Compression Ratio ( up to mid 1936 ) |
4.8 : 1 |
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| Compression Ration ( post mid 1936 ) |
6 : 1 |
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| b.h.p. 1922 |
10 @ 2400 rpm |
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| 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 |
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Timing
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| Pre 1935 |
1 7/8" B T D C |
( 20 degrees ) |
| Mk1 Ruby engine |
3/4" B T D C at flywheel |
points should be just opening. |
| Firing Order |
1 3 4 2 |
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| 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" |
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Valve clearances
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| 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 |
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Big
End Bearings
Standard engine Not pressure fed
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| Big end clearance to crank pin |
0.001" to 0.002" |
Optimum clearance |
| Crank pin out of round |
0.003" |
preferred maximum |
| Big end nuts torque |
around 20 ft. lbs. |
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Small End Bolts
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| Small end bolts |
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Bolt Heads should face off-side of engine |
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Camshaft
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| End float |
0.002" |
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Lubrication
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| Normal Oil Pressure - 2 bearing crank |
up to 5 p.s.i. |
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| Normal Oil pressure - 3 bearing crank |
up to 5 p.s.i. |
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| Oil filter |
Gauze in sump |
clean 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 |
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| Sump capacity sports engine |
8 pints |
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Cooling System
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| Capacity |
9 ½ pints approx. |
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Pistons & Rings
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| Split skirt piston |
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Split on nearside of engine |
| Piston to cylinder clearance |
.0015" |
Split skirt piston |
| Piston to cylinder clearance |
.004" |
Plain skirt piston |
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| Ring Gap |
0.003" to 0.006". |
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