Ford Thunderbird Manual page 33

03-oo-32
SERVICE PROCEDURES (Continued)
Valve Stem-to-Valve Guide Clearance
Check the valve stem-to-valve guide clearance of
each valve in its respective valve guide with Dial
Indicator with Bracketry TOOL -420 1-G and Valve
Stem Clearance Tool TOOL -6505-E or equivalents.
Use a flat-end indicator point.
Install the tool on the valve stem until it is fully seated
and firmly tighten the knurled setscrew. Permit the
valve to drop away from its seat until the tool contacts
the upper surface of the valve guide.
)
Position Dial Indicator with Bracketry TOOL -420 1 -C or
equivalent with its flat tip against the center portion of
the tool's spherical section at approximately 90
degrees to the valve stem axis. Move the tool back
and forth in line with the indicator stem. Take a reading
on the dial indicator without removing the tool from the
valve guide upper surface. Divide the reading by two
which is the division factor for the tool. If valve
stem-to-valve guide clearance exceeds the wear limit,
ream the valve guide for the next oversize valve stem
as described under Valve Guides, Reaming.
Valves, Select Fitting
In the case of valve stem-to-valve guide clearance, the
service clearance is intended as an aid to diagnosing
engine noise only, and does not constitute a failure or
indicate need for service. However, when overhauling
or reconditioning a cylinder head, the service
clearance should be regarded as having a practical
working value, and used to determine installation of the
next oversize valve.
Engine-Service
"' DIAL INDICATOR
WITH BRACKETRY
TOOL-4201-C
3.8L Engine
If the valve stem-to-valve guide clearance exceeds the
service clearance, ream the valve guide for the next
oversize valve stem. Valves with oversize stem
diameters of 0.38 mm and 0. 76 mm {0.0 1 5 inch and
0.030 inch) are available in diameters of 0.4 1 mm and
0.81 mm {0.0 1 6 inch and 0.032 inch) oversize.
Always reface the valve seat after the valve guide has
been reamed. Refer to Valve Guides, Reaming under
Service Procedures, Cylinder Head.
Valve Guide Replacement
4.6L Engine
If the valve stem-to-valve guide clearance exceeds the
service clearance, replace the valve guide. Ream the
valve guide to the standard diameter of 7.02-7.04 mm
{0.276-Q.277 inch). Always reface the valve seat after
the valve guide has been replaced.
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 (0.0 1 0 inch) from the end of
the valve stem.
If the valve face run out 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 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
and replace valve stem seal {657 1).
03-0G-32
1997 Thunderbird, Cougar July 1 996