454 CID (7.4L) / 502 CID (8.2L)
SERVICE MANUAL NUMBER 23
Page 3A-43
90-861326--1 MARCH 1999
IMPORTANT: Excessive valve stem to bore clearance will cause excessive oil con-
sumption and possible valve breakage. Insufficient clearance will result in noisy and
sticky valves.
5. Measure valve stem clearance as follows:
a. Attach a dial indicator to cylinder head, positioning it against the valve stem and
close to the valve guide.
b. Holding valve head off seat about 1/16 in. (2 mm), move valve stem back and forth
in direction shown. Compare stem clearance with specifications.
72563
b
c
a
a -
Dial Indicator
b -
Valve Stem
c -
Valve Guide
c. If clearance exceeds specifications, it will be necessary to ream valve guides for
oversized valves, as outlined under “Valve Guide Bore Repair.”
Valve Guide Bore Repair
IMPORTANT: Be sure to measure valve stem diameter of both the intake and exhaust
valve, as valve stem diameter may or may not be the same for both valves.
If .015 in. oversize valves are required, ream valve guide bores for oversize valves, as fol-
lows:
1. Measure valve stem diameter of old valve being replaced and select proper size valve
guide reamer from chart below.
Standard Valve Stem Diameter
Reamer Required For .015 In. Oversize Valve
.372 In.
J-7049
2. Ream valve guide bores, as shown.
72927
3. Remove the sharp corner created by reamer at top of valve guide.
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