Intake And Exhaust Valve Guide Replacement; Intake And Exhaust Valve Seat Replacement - Lycoming IO-390-D Series Maintenance Manual

J. Ream the valve guide as follows:
(1) Apply force on the reamer to ensure the reamer has gone through the full length of the
valve guide. The 1 in. (2.54 cm) pilot must be visible through the exhaust port or through
spark plug hole using an angled mirror.
(2) Clean the valve guide per the "Hard Carbon Removal" procedure in Chapter 05-30 for
additional cleaning details.
(3) Measure the inner diameter of the valve guide using the correct plug gage.
(4) Examine the reamed hole to see if the reamer has cut all the way to the exhaust port end
of the guide. If it has not, and the exhaust port end of the hole looks dark, the valve guide
is bell-mouthed and must be replaced.
(5) If the valve guide is acceptable, apply lubricant to the valve guide.
CAUTION
K. Install the valves that are satisfactory, in the same position where they were. Refer to the
"Intake Valve Installation" and "Exhaust Valve Installation" procedures in this chapter.
L. Install the valve springs and valve spring seats.
M. Remove and clean the hydraulic lifter and remove all oil. Refer to the "Tappet Cleaning"
procedure in Chapter 05-30.
N. Examine the lifter for any malfunction.
O. Clean the inner diameter of the cam follower.
P. Install the hydraulic lifter.
Q. Install the cylinder and valve train components in the same position as removed. Refer to the
"Cylinder Installation" procedure in this chapter.
R. Install the spark plugs. Refer to Chapter 74-20 for spark plug inspection and installation
instructions.

17. Intake and Exhaust Valve Guide Replacement

Any time a valve guide is to be replaced, send the engine cylinder to an authorized vendor who
can complete this replacement.

18. Intake and Exhaust Valve Seat Replacement

If an intake or exhaust valve (Figure 39) is
damaged or must be replaced, send the
engine cylinder to an authorized vendor
who can complete this replacement.
72-30
Page 228
NEVER USE THE PISTON TO PUSH THE VALVE THROUGH THE
GUIDE.
IO-390-D Series Engine Maintenance Manual
IO-390-D Series Engine Maintenance Manual
Figure 39
Intake and Exhaust Valve Seats
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March 2020