Mack E7 Service Manual page 127

5-101.bk Page 37 Friday, March 17, 2006 11:05 AM
Figure 5-47 — Valve Seat Insert Installation
1. Valve seat insert
2. J 38586
3. Grind inlet/exhaust valve seat inserts to
specification.
Inlet valve inserts before November
1996: 30° –0'/+ 30' angle; November
1996 and later: 20° 30' ± 15' angle
Exhaust valve inserts: 30° –0'/+ 30'
Always use 30-degree valves with 30-degree
valve inserts and 20-degree valves with
20-degree valve inserts. Excessive wear and
possible failure will result if 30-degree parts are
matched with 20-degree parts.
200 BENCH PROCEDURES
3. J 8092
If valve seat insert widths exceed specifications
when grinding inserts, use a 15-degree angle
grinding stone to obtain correct width.
Refer to Figure 5-48.
4. After grinding is completed, thoroughly clean
valve seat insert.
5. Determine concentricity of each valve seat
insert relative to valve guide. Valve seat
runout is to be held within 0.001 (0.025 mm)
FIM (Full Indicator Movement), with finished
valve guide ID measurements made from
snug-fitting arbor (1) and through-mounted
into finished valve guides (2).
6. After valve insert has been ground and
cleaned, determine position of contact area
between valve and valve seat insert. Apply a
dab of Prussian Blue to valve face at four
points, 90 degrees apart.
7. Lower stem of valve into valve guide and
allow valve face to rest on seat insert.
Rotate valve 90 degrees on insert. Carefully
remove valve without making contact with
valve face. Properly ground inserts should
have full pattern on insert.
Thoroughly clean cylinder head after checking
valve seat inserts and before installing valves.
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