Place the rear end plate (45) over the rotor shafts and on the housing, and temporarily secure each end plate
to the blower housing with four screws and flat washers.
e. Install screws (39) and thrust washers (40) in the front end of the blower. Install spacers (38) and thrust plate
(37) and secure with screws (36). Tighten screws (36) to 7--9 ft-lb (-12 N m). Then check the clearance between thrust
plate (37) and thrust washers (40). The specified clearance is 0.001 to 0.003 inch.
Position rotor (43) so that the missing serrations on the gear end of the shafts are 90 apart, as shown in
figure 3-8. This is accomplished by placing the rotors in the shape of a "T" with the missing serration in the upper rotor
facing to the left and the missing serration in the lower rotor facing toward the bottom. Install spacers (35) and shims (31),
(32), (33) and (34) in the counterbore in the rear face of the rotor gear. Then place gears (29) and (30) on the ends of the
shafts with the missing serrations in alignment with the missing serrations on shafts.
g. Tap the gears lightly with a soft hammer to seat the gears on the shafts. Then rotate the gears until the
punch marks on the face of the gears match. If the punch marks do not math, reposition the gears.
Wedge a dean cloth between the blower rotors. Use the gear retaining bolts and flat washers to press the
gears on the rotor shaft. Turn the bolts uniformly until the gears are tight against the shoulder of the shafts.
Remove the gear retaining bolts and washers and place the blower drive cam pilot (28) in the counterbore of
the upper gear and start the gear retaining screws (27) in the rotor shaft. Tighten the bolts to 25--30 ft-lb (34-41 N m).
Check backlash between the blower gear, using a suitable dial indicator. The correct backlash is 0.0005
to 0.0025 inch, for new gears, or a maximum of 0.0035 with used gears.
k. After the rotors and gears have been installed, the blower rotors must be timed. When properly positioned,
the blower rotors run with a sight clearance between the rotor lobes and between the lobes and the walls of the housing.
Clearances between the rotors may be varied by moving one of the gears in or out 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, because a combination of feelers is more flexible. Take the measurements
from both the inlet and outlet sides of the blower.
Measure the clearance between the rotor lobes and the housing as shown in figure 3-8. Take
measurements across the entire length of each rotor lobe to be certain that a minimum clearance of 0.004 inch exists at
the air outlet side, and a minimum of 0.0075 inch at
the air inlet side.
(2) Measure the clearance between rotor lobes,
across the entire length of the lobes. By rotating the
gears, position the lobes so that they are at their closest
relative position. Clearance between lobes should he a
minimum of 0.010 inch.
(3) Measure the clearance between the end of the rotor and the blower end plate through the inlet and outlet
openings. Clearances should be a minimum of 0.006 inch for the front end plate, and .009 inch for the rear end plate.
Push and hold the rotor toward the end plate at which the clearance is being measured.
Remove the screws and washers used to temporarily secure the front end plate to the housing. Then install
gasket (9), cover (8), special washers (6) reinforcement plates (7) and screws (5). Tighten the screws to 20-25 ft- lb (27--4
m. Assemble the blower drive spring support as follows:
(1) Place drive spring support (26) on two blocks of wood.
(2) Position drive spring sea (22) in the support.
(3) Apply grease to springs (21) to hold the leaves together, and then slide the two spring packs in place.
(4) Press drive cam (20) between the spring packs.
n. Install the drive spring support assembly on the rotor gear at the rear end of the blower.
o. Install retainer (17) and secure with screws (16). Tighten the screws to 8-10 ft-lb (11--14 N. m).
p. Remove the bolts and washers used to temporarily secure the rear end plate to the housing, and install gasket
(15), plate cover (14) and secure with screws (11), special washers (6), reinforcement plates (7), lock washers (12) and
flat washers (13). Tighten screws to2-2 5 ft-lb (27-34 N. m).
a. Examine the inside of the blower for any foreign objects. Also revolve the rotors by hand to assure that they
b. Install gasket (4) on the side of the engine block. (Use adhesive only on the block side of the gasket.)
c. Install seal (10) and clamp (1) on the blower rear end plate cover.
d. Slide one end of the blower drive shaft (19) into the drive cam, and position the blower on the side of the engine
block. Use care so as not to damage or dislocate the gasket.
e. Secure the blower assembly to the engine block
with screws (2) and washers (3). Tighten the screws to
55-60 ft-lb (7-81 N m). Install retainer ring (18).
f Slide the seal (10) and clamp (1) back against the