454 CID (7.4L) / 502 CID (8.2L)
SERVICE MANUAL NUMBER 23
Page 3A-45
90-861326--1 MARCH 1999
Regardless of type of equipment, however, it is essential that valve guide bores be free from
carbon or dirt to achieve proper centering of pilot in valve guide, ensuring concentricity.
72568
Measuring Valve Seat Concentricity
Valve Grinding
Valves that are pitted must be refaced to the proper angle. Valve stems that show excessive
wear or valves that are warped excessively must be replaced. When a valve head that is
warped excessively is refaced, a knife edge will be ground on part or all of the valve head
due to the amount of metal that must be removed to completely reface. Knife edges lead
to breakage, burning or pre-ignition due to heat localizing on this knife edge. If the edge of
the valve head is less than 1/32 in. (0.8 mm) after grinding, replace the valve.
Several different types of equipment are available for refacing valves. The recommendation
of the manufacturer of the equipment being used should be carefully followed to attain prop-
er results.
a
a
b
b
50695
Exhaust Intake
a-0.372 In. (9.45 mm)
b-1/32 [.031] In. (0.79 mm) Min.
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