1.3 Crankshaft
DETROIT DIESEL 53
journal holes as shown in Fig.5 Replace the crankshaft
when cracks of this nature are found.
into the journal and the crank cheek, and must be free
of scratches. The radius may be checked with a fillet
gage.
Crankshaft Grinding
4. Care must be taken to avoid localized heating which
often produces grinding cracks. Cool the crankshaft
In addition to the standard size main and connecting rod
while grinding, using coolant generously. Do not crowd
bearings, .002", .010, .020" and .030" undersize
the grinding wheel into the work.
bearings are available.
5. Polish the ground surfaces to an 8-12 R.MS. finish.
NOTE: The .002" undersize bearings are
The reground journals will be subject to excessive wear
used only to compensate for slight wear on
unless polished smooth.
crankshafts on which regrinding is
unnecessary.
6. If the thrust surfaces of the crankshaft are worn or
grooved excessively, they must be reground and
If the crankshaft is to be reground, proceed as follows:
polished. Care must be taken to leave a .100" to .130"
radius on the 6V engine, between each thrust surface
1. Compare the crankshaft journal measurements taken
and the bearing journal (Fig. 7).
during inspection with the dimensions in Table 1 and
Fig. 6 and determine the size to which the journals are
7. Stone the edge of all oil holes in the journal surfaces
to be reground.
smooth to provide a radius of approximately 3/32".
Measurement of the crankshaft journals, and
8. After grinding has been completed, inspect the
comparison of these measurements to the diameters
crankshaft by the magnetic particle method to determine
required for various undersize bearings shown in Fig. 6
whether cracks have originated due to the grinding
and Table 1, will determine the size to which the
operation.
crankshaft journals must be reground.
9. Demagnetize the crankshaft.
2. If one or more main or connecting rod journals
require grinding, then grind all of the main journals or all
10. Remove the plugs and clean the crankshaft and oil
of the connecting rod journals to the same required size.
passages thoroughly with fuel oil. Dry the shaft with
compressed air and reinstall the plugs.
3. All journal fillets must have a .100" to .130" radius
between the crank cheek and the journal, and must not
Install Crankshaft
have any sharp grind marks (Fig. 7). The fillet must
blend smoothly
If a new crankshaft is to be installed, steam clean it to
remove the rust preventive, blow out the oil passages
with compressed air and install the plugs. Then, install
the crankshaft as follows:
NOTE: When a new or reground crankshaft is
TABLE 1
TABLE 2
1972 General Motors Corp.
Page 6
