DS 19 OPERATION No. DS 100-3 : Overhauling an engine. Op. DS 100-3 45
PARTICULAR POINTS
Dismantling.
11 When removing the assembly of the crankshaft, connecting rods and pistons, make sure that the order and direction of assembly of the
central bearing is marked. If the crankshaft and bearings are to be re-used make a reference mark so that they are not reversed on
assembly.
16 Do not remove the connecting rod small end bushes.
17 The cylinder head, being made of aluminium, one cannot remove the sparking plug tubes or valve seats without the use of special tools. It is
possible to replace the valve guides (see Op. DS 112-3).
If a thread is damaged it is possible to replace it by a "Heli-coil" thread (see note MR-4279).
Assembly.
23 Characteristics of the valve springs.
Outer springs. L = 37 mm under load of 24.200 ± 1.350 kg and L = 28.5 mm under load of 52 ± 2.800 kg.
Inner springs. L = 24.5 mm under load of 5.250 ± 0.300 kg and L = 16 mm under load of 11 ± 0.600 kg.
Do not fit the rubber seal on the exhaust valves.
24 Check the oil pump on a test bench.
With S.A.E. 20 engine oil at 60˚ C. and the pump outlet through a jet of 2.8 mm dia. the pressure should be at 1000 r.p.m. equal to 50 p.s.i.
(3.5 kg/cm
2
).
25 To fit a starter gear ring on the flywheel.
Heat the bore of the starter gear ring to a temperature of 200 to 250˚ C (straw colour). Do not exceed this temperature.
26 If the clutch bearing face "a" has been ground, remove the same amount from the bearing face "b" of the clutch casing (see Pl. 42). The
distance between the bearing face of the crankshaft and the face of the Ferodo disc should not be less than 15.4 mm.
27 To prepare the parts for the crankshaft.
The tightening torsion of the bearing cap screws is 58 ft./lb. (8 m.kg), admissible clearance = 0.06 mm max. between the crankshaft and
bearings.
The tightening torsion of the connecting rod screws is 36 ft./lb. (5 m.kg), admissible clearance = 0.06 mm max. between the crankshaft and
the connecting rods.
Note the reference marks made when dismantling the bearings and caps.
29 To fit the pistons: heat the piston to 60°C (oil bath) in order to fit the gudgeon pins, note the order of assembly, do not interchange the pins.
30 The tightening torsion of the connecting rod screws is 36 ft/lb (5 m.kg). This tightening torsion must be strictly adhered to.
31 Tighten the fixing screws of the camshaft rear thrust plate to 7.5 ft/lb (1 m.kg) (lockwashers).
33 Fitting the cylinder barrels: adjust their height with one paper joint only.
Cylinder head gasket: smear with boiled linseed oil, the crimping towards the barrels; the new type gasket should be fitted dry, the varnished
side towards the cylinder head.
34 Fitting the cylinder head: First tightening 21.75 ft/lb (3 m.kg), second tightening 43.5 ft/lb (6 m.kg). Observe the tightening torsion and order
of tightening the screws indicated on Pl.7.
Check the bores of the cylinder barrels: deformation or ovality = 0.03 mm max., except for 20 mm at the bottom of the cylinder barrel: 0.05
mm max.
35 Oil seals: Insert a shim steel strip (L = 200, 1 = 10, thickness 0.1 mm) around the oil thrower and tighten the fixing screws of the half-shells.
Remove the bearing cap and remove the shim. Refit the new assembly.
Tighten the bearing cap fixing screws to 72 ft/lb (10 m.kg).
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