莱康明发动机大修手册 OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES(21)

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5-38. Inspect the hydraulic lifter for evidence of the following wear patterns:
a Spalling - If the face of the lifter shows small nicks or indentations near the center of the face it is considered pitted or spalled. The pitting will constitute small ir- regular holes. not to be confused with Rockwell hard-ness check marks. which are round and even. The area covered by spalling will vary with different lifter. but regardless of the degrees of spalling the lifter must be replaced.
b.
Scoring-The lifter face is scored when small scratch- like lines are found near the outer edge of the face and will appear to radiate from the center. Other scoring marks may be present and extend to the center of the face. The lifter with this condition must be replaced.

c.
Lifter Face Wear-The operation of the lifter provides that the lifter rotates during the wiping action of the camshaft lobe. This action will form a groove or path across the face of the lifter. Deeper penetration will be noted at the center of the face. If the wear is excessive it will be noticeable to the touch. if a fingernail is rubbed across the lifter face. This condition reguires replace ment of the lifter.

Figure 5.9. Method of Checking Valve Edge
Thickness with Dial Indicator

OVERHAUL MANUAL LYCOMING 76SERIES AIRCRAFT ENGINES Section5
NOTE

Indications of non rotation of the hydraulic lifters is not cause for rejection unless the lifter face is marked as described in Par. 5-38 a, b or c.
5-39. When the hydraulic lifter is rejected because of spall-ing or scoring, a visual inspection of the nose of the cam lobe with a magnifying glass (min. 10 power) must be made. Any indication of distress surface irregularity, or feathering of the edge of the cam lobe is cause for rejec-tion of the camshaft.
NOTE

Whenever the camshaft is replaced, either with one that is reconditioned by grinding the cam lobes or a new cam-shaft. all hydraulic lifters must be replaced with new lifters.
5-40. Valve Springs. Check the condition of all valve spr-ings on a suitable spring tester, using the loads and deflec-tions as given in reference 800 and 801, Table of Limits.
REPAIR AND REPLACEMENT

5-41. General instructions for the repair of cylinder, piston and valve train parts will be found in Section 3. Specific instructions follow.
5-42. Spark Plug Thread Insert. Spark plug thread inserts which were rejected during inspection are removed and replaced as described in the following paragraphs.
5-43. Insert the extracting tool (64595) in the spark plug hole so that the edges of the tool cut into the top thread of the insert. Rotate the tool in a counter-clockwise direc-tion, unscrewing the insert from the hole.
5-44. A new insert may be installed by use of the inserting tool (64594). Withdraw the mandrel part of the tool beyond the recessed section of its sleeve. The insert may then be assembled into the recess and the mandrel ad-vanced to engage its slotted end with the tang of the in-sert. Rotate the mandrel clockwise and press forward
　
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