莱康明发动机大修手册 OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES(18)

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1. Cracked fins.
(a) Fin adjacent to the exhaust port flange.
(1)Stop drilling, a 3/16 inch diameter hole through the end of the crack is permissible providing the end of the crack is at least 1/4 inch from the base of the metal.
(2) Fin removal to eliminate crack and reduce vibrating mass is permitted provided:
aa. Maximum removal is no more than one half the total fin width.
cc. No burrs or sharp edges are permitted.
dd. Minimum fillet at the root of the removed portion of the fin in one quarter inch radius. Minimum corner at top of fin adjacent to the removed portion is one half inch radius.

(b) Fins other than the above may be accepted provided not more than one crack per fin and its depth is no closer than 1/4 inch from the base of the metal and a fin stabilizer is used to reduce vibration and further deepening of the crack.
2. Physically damaged, broken or bent fins.
(a)The blended area for any one fin shall not exceed 3/8 square inches, nor 3/8 inch in depth.
(b) No more than two blended areas on any one fin.
(c)No more than four blended fins on the push rod side of the head. No more than six blended fins on the anti-push rod side of the head.
(d)
In addition to the above, it is recommended that a fluorescent penetrant inspection of the cylinder be made. Pay particular attention to the following areas.

(1)
Between the 15th and 20th cylinder fin (counting from the top) on exhaust port side of cylinder.

(2)
The area around the lower spark plug counterbore.

5-23. Cylinder Head (Dimensional Inspection). Check the ID of each intake valve guide (it is recommended that ex-haust valve guides be replaced at overhaul) with the flat plug rejection gage (ST-81). Check the diameter and out-of-roundness of the guide bore by checking with the gage at a minimum of two position 900 apart. If the gage enters the guide at any of the positions tested, mark the guide for replacement.
5-24. Cylinder Barrel (Visual Inspection). In addition to a thorough inspection of the cylinder barrel to ascertain its general condition, make the following specific checks.
THIS PART OF PISTON HAS LARGER DIAMETER THANRINGLANDS. STRAIGHTEDGEMUST
BEUSED AS SHOWN
FEELERGAGE
STRAIGHT EDGE
Figure 5-5. Method of Checking Piston Ring Side Clearance

OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES Section5
a.
Cooling Fins. It is recommended that notches or nicks be profiled with a hand grinder or file. A cracked cylinder barrel is cause for rejection of the cylinder.

b.
Cylinder Skirt. Replace any cylinder having a bent, cracked,

broken or corroded skirt,

c.
Check mounting flange for cracks, nicks, warping, or corrosion.

d.
Inspect interior of barrel for scoring or corrosion. Minor damage can be repaired by regrinding or honing; deep scoring or pitting, however, is cause for rejection of
　
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