slightly; this will engage the insert in threaded end of sleeve. Continue to rotate the mandrel while holding the sleeve thus securing the insert firmly on the inserting tool. The insert may then be wound through the threaded portion of the sleeve within one half turn from the end of the coil.
5-45. The adjustable brass screw on the sleeve tends to act as a brake, preventing the insert from unwinding. It is im-portant that the insert be kept tight on the mandrel to facilitate its assembly in the threads of the cylinder head. The insert should be wound so that the adjacent turns of the insert are in contact with each other. This will eliminate the possibility of crossed threads.
NOTE
When inspection reveals the necessity of replacing a spark plug heli-coil insert it must be replaced with a .010 inch oversize insert. A .010 inch bottoming tap (64596-1) is available.
5-46. When screwing the insert into the hole in the cylinder head, be sure that the first coil picks up the first thread. As the tool is turned,the insert will advance into the hole. When the face of the sleeve is approximately 1/16 inch from the face of the boss, the inserting tool should be held tightly by the handle and the sleeve rotated counter-clockwise with the other hand, freeing the last half-turn of the insert. By sliding the sleeve toward the top of the mandrel, the end of the insert can be seen projecting above the boss. The mandrel should then be rotated in a clockwise direction until the insert disappears from sight. When this position is reached, the turning action should be stopped and the tool withdrawn. The top of the insert will be approximately one half turn from the face of the
boss. However, if it is not, the tool should be reassembled and the insert turned until it is about one half turn from
the face of the boss.
5-47. The tang of the insert can be broken off with needle-nose pliers at the location of the notch. Then using the ex-panding tool (64593), secure the insert firmly in the spark plug holes. The limit of expansion can be kept within the thread gage limits by fixing the stop nut on the
°
15
MODEL "A" INTAKE "B" EXHAUST "C" INTAKE "D" EXHAUST
0-320-H 2.154/2.155 1.740/1.750 .076/.117 .058/.077O, LO-360-E 2.154/2.155 1 740/1 7.50 076/ 117
.076/.117 .058/.077
Figure 5-10. Valve Seat Dimensions for Reconditioning
Section5 OVERHAUL MANUAL
LYCOMING 76 SERIES AIRCRAFT ENGINES
Cylinder,Piston
andValveTrain expanding tool at the correct position. After expanding
panding the insert, it may be staked by assembling the staking sleeve over the mandrel until the sleeve meets the boss. A slight blow on the top of the sleeve will impress a slight chamfered edge around the periphery of the tappedd holes. The staking sleeve may then be removed and adjusting screw released, and the expanding mandrel removed
ed from the insert.
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