DETROIT DIESEL 53
bolts and plain washers.
6. Attach the two thrust washers to the front end of the blower
with the washer retaining bolts. If 5/16 "-24 bolts are used, tighten
them to 25-30 Ib-ft torque; if 3/8 " - 24 bolts are used, tighten
them to 54-59 Ib-ft torque.
7. Attach the three spacers and the thrust plate to the front end
of the blower. Tighten the three bolts to 7-9 lb-ft torque. Then
check the clearance between the thrust plate and the thrust
washers. The specified clearance is .001 " to .003 ".
NOTE: The current thrust plate is .260 " thick. The former plate
was .180 " thick.
8. Position the rotors so that the missing serrations on the gear
end of the rotor shafts are 90 ° apart. This is accomplished by
placing the rotors in a "T" shape, with the missing serration in the
upper rotor facing to the left and the missing serration in the lower
rotor facing toward the bottom (Fig. 14). Install the shims and
spacers in the counterbore in the rear face of the rotor gears.
Then place the gears on the ends of the shafts with the missing
serrations in alignment with the missing serrations on the shafts.
Fig. 16 - Measuring Rotor Lobe to End Plate
9. Tap the gears lightly with a soft hammer to seat them on the shafts. Then rotate the gears until the punch marks on
the face of the gears match. If the marks do not match, re-position the gears.
10. Wedge a clean cloth between the blower rotors. Use the gear retaining bolts and plain washers to press the gears
on the rotor shafts (Fig. 13). Turn the bolts uniformly until the gears are tight against the shoulders on the shafts.
11. Remove the gear retaining bolts and washers. Then proceed as follows:
3-53 Blower-- Place the gear washers on the gears and start the gear retaining bolts in the rotor shafts. Tighten the
bolts to 25-30 Ib-ft torque.
12. Check the backlash between the blower gears, using a suitable dial indicator. The specified backlash is .0005 " to
.0025 " with new gears or a maximum of .0035 " with used gears.
13. Time Blower Rotors
After the blower rotors and gears have been installed, the blower rotors must be timed. When properly positioned, the
blower rotors run with a slight clearance between the rotor lobes and with a slight clearance between the lobes and the
walls of the housing.
The clearances between the rotors may be established by moving one of the helical gears out or in on the shaft relative
to the other gear by adding or removing shims between the gear hub and the rotor spacers. It is preferable to measure
the clearances with a feeler gage comprised of two or more feelers, since a combination is more flexible than a single
feeler gage. Take measurements from both the inlet and outlet sides of the blower.
Measure the clearance between the rotor lobes and
JULY, 1972 SEC 3.4 PAGE 9