Vanguard BIG BLOCK M540000, Repair Manual, Page: 92 / 168

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4. Repeat the 6 point check outlined under step 3 to check
for warpage or distortion of the cylinder head to valve
cover mating surfaces. Be sure to check both the cylinder
head and valve cover. Discard the cylinder head or valve
cover if any low spot is 0.002 inches (0.05 mm) or more.
5. Visually inspect the cylinder head for cracks or
discoloration due to excessive heat. Replace cylinder
head if either of these conditions are found.
6. Verify that breather hole, and intake and exhaust ports
are clean and open.
Valve Guide Inspection
1. Inspect external surface of valve guides for cracks
(particularly the combustion chamber side). Replace the
cylinder head if cracks are found.
2. To verify cleanliness, lightly hone bore using a suitable
valve guide hone and then scrub with a valve guide
cleaning brush to remove any dirt or debris.
3. Measure the inside diameter using an inside ball
micrometer or plug gauge. Replace the cylinder head if
the measurement is 0.240 in (6.106 mm) or more.
Valve Seat Inspection
1. Inspect valve seats for cracking, chipping or burning.
Replace cylinder head if any of these conditions are
found or if either valve seat is loose.
Valves
1. Replace the valve if bent or if there is evidence of
burning or cracking.
2. Inspect the end of the valve stem for pitting or uneven
wear. Replace the valve if either of these conditions are
found.
3. Inspect the valve stem retainer groove for burrs, damage
or excessive wear. Remove burrs with a fine tooth file if
found.
4. Polish the valve stem with fine emery cloth or steel wool
to remove carbon buildup.
5. Measure the top, center and bottom of the intake valve
stem using an outside micrometer ( A , Figure 110).
Replace the intake valve if any measurement is 0.228 in
(5.791 mm) or less.
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6. Measure the top, center and bottom of the exhaust valve
stem. Replace the exhaust valve if any measurement is
0.228 in (5.791 mm) or less.
7. Hold each valve against a worn wire wheel in a bench
grinder to remove all carbon deposits from the valve
head and face, but exercise caution to avoid removing
any metal material.
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