Lycoming TEO-540-C1A Maintenance Manual page 214

(2) Measure and cut a total of four continuous lengths of "00" silk threads (four for only one
crankcase half). Two of the lengths will extend along the entire length of the top of the
crankcase flange as shown in Figure 90, and two silk thread lengths will be shorter to
cover the distance shown on the bottom flange of the same crankcase half. Do not apply
silk thread pairs to both crankcase halves.
Area on the Crankcase Flange to Apply
the POB Sealant and Silk Thread
CAUTION
(3) Press two lengths of "00" silk threads in the gasket compound on the top and bottom
flange sides (of the crankcase half) (Figure 90) firmly in the gasket compound where both
silk threads are oriented in the area between the bolt holes and the inside flange edge of
the crankcase half (approximately between 0.020 to 0.040 in. (0.508 to 1.106 mm)) apart
as shown in Figure 91. Make sure that the silk thread lengths do not touch or cross over
one another or cover a bolt hole.
(4) All continuous silk thread lengths must extend not more than ¼-in. (6.35 mm) beyond the
front and rear end of the crankcase half. Figure 92 shows the correct thread overhang
extension into the seal groove on the front end of the crankcase half. Figure 93 shows the
silk thread overhang extending from the rear of the crankcase half.
Figure 92
Silk Thread Extending into Seal Groove on
the Front End of the Crankcase
72-20
Page 184
Figure 90
TO ENSURE CORRECT SEALING, MAKE SURE THE SILK
THREADS RUN THE LENGTH, EACH THREAD AS A
CONTINUOUS PIECE, OF THE INSIDE OF THE CRANKCASE
FLANGE (FIGURE 90) AND THERE ARE NO BREAKS IN ANY OF
THE THREADS. BREAKS IN THE SILK THREAD CAN CAUSE THE
CRANKCASE TO LEAK.
TEO-540-C1A Engine Maintenance Manual
TEO-540-C1A Engine Maintenance Manual
Placement of Silk Threads Along
Inside Edge of Crankcase Flange
Figure 93
Silk Thread Extending into the
Rear End of the Crankcase
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Figure 91
November 2018