03-0G-33
Engine-Service
03-0G-33
SERVICE PROCEDURES (Continued)
Valve Guides, Reaming
3.8L Engines
CAUTION: Always reface the valve seat after the
valve guide has been reamed and use a suitable
scraper to break the sharp corner (ID) at the top
of the valve guide. Failure to do so may result in
possible valve train wear and/ or damage.
If it becomes necessary to ream a valve guide to install
a valve with an oversize stem, a hand-reaming kit is
available which contains the following reamer and pilot
combinations: a 0.38 mm (0.0 15 inch) OS reamer with
a 0. 76 mm (0.03 inch) OS pilot, and a 0. 76 mm (0.03
inch) reamer with a 0.38 mm (0.0 15 inch) OS pilot.
When replacing a standard size valve with an oversize
valve, always use the reamer in sequence (smallest
oversize first, and then next smallest and so forth) so
reamers will not be overloaded.
NOTE: If oversize valve stems and oversize valve
stem seal are not available, press out original guide
and install service bushing. Ream ID for specified
clearance for standard-size valve. Reface valve seat
as required. Install standard-size valve stem seal.
CAUTION: The interference angle of the valve
and seat should not be lapped out. Remove all
grooves or score marks from the end of the valve
stem and chamfer it as necessary. Do not remove
more than 0.254 mm (0.01 0 inch) from the end of
the valve stem or excessive valve clearance may
occur.
If the valve face runout is excessive and
I
or to remove
pits and grooves, reface the valves to a true
45-degree angle. Remove only enough stock to
correct the runout or to clean up the pits and grooves.
If
the edge of the valve head is less than 0. 794 mm
(0.03 1 inch) thick after grinding, replace the valve
because the valve will run too hot in the engine.
If the valve and
I
or valve seat has been refaced, check
the clearance between the rocker arm pad and the
valve stem with the valve train installed in the engine.
Valve Seats, Refacing
Measure the valve seat width. Reface the valve seats
if the width is not within specifications. Refer to
Section 03-Q1 A (3.8L) or Section 03-Q1B (4.6L) for
Specifications.
Refer to Engine Service Section in the Rotunda Tool
catalog for a description of the various valve seat
grinders and cutters available.
Refacing the valve seat should be closely coordinated
with the refacing of the valve face so that the finished
seat and valve face will be concentric and the
specified interference angle will be maintained. This is
important so that the valve and seat will have a
compression-tight fit. Make sure refacer grinding
wheels are properly dressed.
Grind the valve seats to a true 45-degree angle.
Remove only enough stock to clean up pits and
grooves or to correct the valve seat runout. After the
seat has been refaced measure valve seat contact
width as described.
The finished valve seat should contact the
approximate center of the valve face. Determine
where the valve seat contacts the face.
To do this, coat the seat with Prussian Blue and set the
valve in place. Rotate the valve with light pressure.
If
the Prussian Blue is transferred to the center of the
valve face, the contact is satisfactory. lf the Prussian
is transferred to the top edge of the valve face, lower
the valve seat. If the Prussian Blue is transferred to the
bottom edge of the valve face, raise the valve seat.
Valves
The critical inspection points and tolerances of the
valve are illustrated. Refer to Specifications in Section
03-0 1 A (3.8L) or Section 03-0 1 B (4.6L) for service
limits.
Valves, Inspection
Inspect the valve stem for bends and the end of the
stem for grooves or scoring.
Inspect the valve face and the edge of the valve head
for pits, grooves or scores. Inspect the stem for bends
and the end of the stem for grooves or scores. Check
the valve head for signs of burning, erosion, warpage
and cracking. Minor pits, grooves and other abrasions
may be removed. Discard severely damaged valves.
Inspect the valve spring (65 1 3), valve spring retainers
(65 14), valve spring retainer keys (65 18) and discard
any damaged parts.
1997 Thunderbird, Cougar July 1996
Содержание Thunderbird
Страница 2: ...This page intentionally left blank Get it ...