DS 19 OPERATION No. DS 100-3 : Overhauling an engine 52
TOOLS
27 To prepare the parts for the crankshaft (see Pl. 13)
In general proceed by renewing the parts.
Nevertheless some repairs are possible.
a) Crankcase :
If the bearing caps have been filed by unskilled repairers, it is not possible to fit the standard crankshaft –
connecting rod assemblies. It will be necessary to renew the cylinder block, or failing this, the cylinder
block bearings must be rebored. To do this :
On a surface plate, check that the bearing faces of the caps are in alignment. If necessary, retouch them with
a file or better still, on a milling machine. Place the bearing caps (without the bearings) on the cylinder block
and tighten the screws to 58 ft/lbs (8 m.kg) (spanner 2471-T, see Pl. 7, fig. 2).
Using a dial gauge (dial gauge 2440-T) measure the diameter “a” (see fig. 2).
Make sure that the dimension “a” measured at one of the extremities of the bearings is the same as dimension
“b” measured at the other extremity. If this is not the case, the bearing faces of the cap are not parallel to the
centre line of the crankshaft, it is necessary to correct them with a file or better still a milling machine.
The difference between the two dimensions “a” and “b” should not exceed 0.01 mm.
Continue again by taking the diameter “a”.
The difference between this diameter “a” and the original dimension (58.01 +
0.025
mm) represents the
0
thickness “e” of the shims to be placed between the cap and the cylinder block (see fig. 2) :
The shims must be machined with the greatest care. Their faces must be parallel within 0.01 mm.
Again fit the caps without the bearings, but this time fitting the shims, tighten the screws to 58 ft/lbs (8 m.kg)
and measure the dimension “a”. It must be
(58.01 +
0.025
mm); if not, correct the shims.
0
We strongly advise this method which, while taking longer, allows the use of the standard crankshaft
– connecting rod assemblies, sold by our Spare Parts Department, without any reworking. We definitely
Prohibit the taking up of the clearance of these assemblies. The clearance is measured with very great Dial gauge 2440-T
precision at the works and cannot be modified without risk of damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Torsion spanner 2471-T
b) Crankshaft :
If necessary a better finish of the bearings can be obtained by lapping them slightly, provided that the
following maximum clearances are adhered to :
on the crankshaft bearing : 0.06 ..
On the connecting rods : 0.06
With a micrometer, measure the diameter of the bearings; they should be :
On the crankshaft main bearings :
54 -
0
mm or 53.5 -
0
mm.
-0.015 - 0.015
On the bearing for the connecting rod :
48.01
-0.01
. mm.
-0.02
"e"= 58.01+
0.025
0
− a.
To Next Page
Loading...
