5-72. Assembly of Pistons. Figure 5-2. Using the piston
ring expander, assemble the new rings on pistons in the order described in the following paragraphs.
OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES Section5
Cylinder,Piston and Valve Train
5-73. With the piston lying top up on the workbench, in-in paragraph 3-39. Apply to inside of cylinder barrel and stall the oil regulating ring equalizer in the first groove to piston and rings working the oil mixture around the above the piston pin hole. Assemble the regulating ring (8) rings and into groove. Starting with no. 1 cylinder proceed
over the equalizer with its gap 180 opposite the equalizer to install as follows: gap. Compress the assembly several times with the fingers to make sure the ring lies free and loose in the 5-79. Rotate crankshaft so that no. 1 piston, when install-groove. Both the equalizer and the regulating ring are ed. will be approximately at top dead center on the firing symmetrical and may be installed with either side up-stroke: this is determined by both tappets of no. 1 ward. cylinder being on the base circle of the cam lobes. Before
any attempt is made to rotate the crankshaft support the 5-74. Install the compression rings (9) in the remaining connecting rods as shown in figure 5-3. top grooves. The compression rings are etched on one side
with the word "top", this side must be installed toward 5-80. Figure 5-2. Assemble piston on connecting rod with the top of piston. piston number, which is stamped on bottom of piston
head, toward the front of the engine. The piston pin (10) 5-75. Pistons. Upon completion of assembly of the piston should be palm or hand push fit. If the original piston pin ring, check the side clearance of the rings in the grooves. is tighter than a palm push fit, it is probably caused by Use feeler gage and straight edge as shown in figure 5-5. nicks or slight carbon in the piston pin bore of the piston.
If a new piston pin or piston is to be installed, select the NOTE pin to give a palm push fit at room temperature of 15 to
20 C. (60 to 70 F.). After piston pin is in place and central-Under no circumstances should oversize piston rings be ly located, insert a piston pin plug (7) at each end of the used in chrome plated barrels. piston pin.
5-76. Assembly of Cylinder. See figure 5-1. Coat the valve guides and valves with a pre-lubricant as described in paragraph 3-39. Insert the intake (18) and exhaust valve
(19) in their respective guides. The intake valve can be identified by the fact that it is slightly larger than the ex-haust valve. Hold the end of the valve stems and place the cylinder on the applicable cylinder holding block. Install on each valve a lower spring seat (22). outer (23) and aux-iliary valve spring (24), and upper valve spring seat (25).
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