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IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
(20) Insert the screwdriver between the
Gage (ST-310) and valve spring on
the opposite side and push the valve
spring toward the dial indicator as
shown in Figure 9.
(21) Relax the screwdriver and record the
reading on the dial indicator. For the
exhaust valve guide to be acceptable,
the measurement must be within the
specified limits in latest revision of
the Service Table of Limits - SSP-
1776.
(22) If the exhaust valve guide is out of
tolerance either replace the cylinder
or send the cylinder to an authorized
vendor who can replace the valve
guide.
(23) Move the piston to near its top end of travel.
(24) Remove the Gage Adapter (ST-310-9) from the valve stem.
(25) Loosen each cap screw in the Gage (ST-310) (Figure 6) in small equal increments to
decrease pressure on the valve spring slowly and equally.
(26) Remove the Gage (ST-310) from the cylinder.
(27) Repeat this exhaust valve and guide inspection for all cylinders.
(28) Record all of the results in the 1000-Hour Inspection Checklist for IO-390-D Series
engines (Chapter 05-20).
CAUTION
(29) If removed, examine and install acceptable plunger assemblies and hydraulic lifter
sockets in the correct location. Refer to the latest revision of Service Instruction SI-1011
for plunger assembly inspection guidelines.
(30) Install all of the seals, washers, sleeve, springs,
shroud tubes, and push rods (Figure 5) on the
cylinder.
NOTICE: The valve stem cap is only on the exhaust
valve stem.
(31) Install the valve stem cap (Figure 10) on the
exhaust valve stem.
(32) Install the rocker assembly, valve rocker shaft
bushing, washer, and valve rocker shaft (Figure 5).
© 2020 Avco Corporation. All Rights Reserved
March 2020
DO NOT MIX PLUNGER ASSEMBLIES WITH DIFFERENT PART
NUMBERS IN THE SAME ENGINE. DIFFERENT PLUNGERS
HAVE VARYING LEAK DOWN RATES WHICH CAN CAUSE
INCORRECT ENGINE OPERATION.
Figure 9
Pushing Valve Stem and Adapter Post
Toward Dial Indicator
Exhaust Valve Stem Cap
Figure 10
72-30
Page 203
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