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2. Install the compression rings (23) in the proper grooves
with the bevel or "pip" mark (if any) toward the top of the
piston. (Refer to Figure 14.)
Check the ring side clearance of each ring in the piston ring
groove. (Refer to Figure 12.) If the side clearance is too
large, the piston ring groove is worn beyond specifications
and the piston must be replaced.
Rotate the piston rings in their respective groove so that
each end gap is at least 90 degrees from the previous ring's
end gap.
Lubricate the wrist pin (22) and wrist pin bushing in the con-
necting rod with engine oil. Assemble the upper portion of
the connecting rods and the pistons with the wrist pins.
Insert the wrist pin buttons (28) in the ends of the wrist pin.
Lubricate the pistons and rings with engine oil. Using a ring
compression tool return the piston to the cylinder bore.
Turn the crankshaft so that one of its connecting rod jour-
nals is in the downward, center position. Install the crankshaft
journal bearing segments (38) on the connecting rod (37)
and connecting rod cap (39). Tighten the connecting rod
bolts (40) evenly and torque to 150 - 170 inch pounds. In-
stall the other connecting rod and piston in the same manner.
It is recommended that new connecting rod cap screws be
used.
Before replacing the cylinder head on the crankcase ensure
the correct pistons have been used by turning the crank-
shaft one complete revolution such that each piston moves
to its maximum upward stroke. At the maximum upward
stroke position each piston should move to the top of the
crankcase. If the piston does not approach the top of the
crankcase the piston is incorrect, and if not replaced, could
result in compressor damage.
BASE PLATE OR BASE ADAPTER
Position the base plate or base adapter gasket (20) on the
crankcase and install the base plate or base adapter (21)
as marked before disassembly. Tighten the six cap screws
(22), securing the cast iron base adapter evenly to a torque
of 175-225 inch pounds for base plate or cover in a crossing
pattern after first snugging all 6 screws.
CYLINDER HEAD
Place the cylinder head gasket (19) and cylinder head on
the compressor crankcase and install the six cylinder head
cap screws. Snug the cylinder head cap screws prior to
torquing the cap screws to 300-360 in. Ibs. in a cross pat-
tern. Retorque the unloader cover cap screws to 170-225 in.
Ibs.
FINAL COMPRESSOR ASSEMBLY
Install all crankshaft keys making certain to support the
crankshaft to avoid bearing damage. Install the crankshaft
nut where applicable. When installing drive couplings or gears,
do not exceed 120 foot pounds torque on the crankshaft
nut.
Use covers, plugs, or masking tape to protect all ports if
compressor is not to be installed immediately. Protect the
ends of the crankshaft against damage by wrapping with
masking tape or friction tape.
TESTING REBUILT COMPRESSOR
In order to properly test a compressor under operating con-
ditions, a test rack for correct mounting, cooling, lubricating,
and driving the compressor is necessary. Such tests are
not compulsory if the unit has been carefully rebuilt by an
experienced person. A compressor efficiency or build up
test can be run which is not too difficult. An engine lubri-
cated compressor must be connected to an oil supply line
of at least 15 P.S.I. pressure during the test and an oil return
line must be installed to keep the crankcase drained.
Connect to the compressor discharge port, a reservoir with
a volume of 1,500 cubic inches, including the volume of the
connecting line. With the compressor operating at 2,100
R.P.M., the time required to raise the reservoir(s) pressure
from 85 psi to 100 psi should not exceed 5 seconds. During
this test, the compressor should be checked for gasket leak-
age and noisy operation, as well as unloader operation and
leakage.
If the compressor functions as indicated reinstall on the
vehicle connecting all lines as marked in the disassembly
procedure.
®
TU-FLO
750 AIR COMPRESSOR
SPECIFICATIONS
Average weight ............................................................ 53
Number of cylinders ...................................................... 2
Bore size ............................................................. 2.78 In.
Stroke .................................................................. 1.87 In.
Displacement at 1250 RPM .............................. 16.5 CFM
CFM Maximum recommended RPM .............. 2,400 RPM
Minimum coolant flow (water cooled) at
Maximum RPM ................................................. 2.5 GPM
Minimum RPM ..................................................... 5 GPM
Approximate horsepower required at
1250 RPM at 120 PSIG (naturally aspirated) .............. 3.2
Turbocharge limits
See Compressor Turbocharging Parameters
Maximum inlet air temperature ............................... 250°F
Maximum discharge air temperature ...................... 400°F
Minimum pressure required to unload
(naturally aspirated) ............................................ 60 PSIG
13
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