OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES Section5
ylinder,Piston aiandValveTrain Cylinder,Piston
TABLE 5-1
VALVE SEAT REPLACEMENT TOOLS VALVE SEAT RECESS CUTTER ID Valve Seat Hole in Cylinder Head
Part No.
1.733-1.735
ST-52,-1,-2,-32.087-2.089
ST-57-1,-2,-3
-1 Indicates .010 inch oversize
-2 Indicates .020 inch oversize
-3 Indicates .030 inch oversize
VALVE SEAT RECESS CUTTER PILOT
ID Valve Guide Hole in Cylinder Head Part No. .5913-.5923
ST-66-1,-2,-3,-5.6613-.6623 ST-67-1,-2,-3,-5
ST-66 is standard ST-66 is standard -1 Indicates .010 inch oversize -3 Indicates .030 inch oversize-2 Indicates .020 inch oversize
-5 Indicates .005 inch oversize VALVE SEAT REPLACEMENT DRIFT ID of Valve Seat Part No. 1.870-2.060
ST-641.474-1.730
ST-65 VALVE SEAT REPLACEMENT FIXTURE
Part No. Parallel Valve Cylinder Heads ST-250
VALVE SEAT RECESS CUTTER DRIVER
Used with all ST series cutters Hand Drive adapter
5-59. Heat the cylinder to 400 to 425°F. and secure to ap-plicable replacement fixture. Chill new seat and place on replacement drift (see Table of 5-1 for correct drift) and drive seat into the recess in the cylinder head by tapping end of drift with hammer.
5-60. Proceed to grind the faces of the newly installed valve seats as described in paragraphs 5-48 thru 5-50.
NOTE
Whenever a new valve seat is installed, it is required that its matching valve guide be replaced. This will assure con-centric grinding of the new seat.
5-61.Valve Refacing. Place valve in a suitable valve refac-ing machine (Snap-On VR-300) or equivalent. Set refacer to 30 for intake valves and 45 for exhaust valves. Using a soft no. 80 grit wheel, remove no more metal than is necessary to clean up pits in the valve face or to correct any apprarent warping condition. Round off with a hand stone any sharp or burred edges left around the valve face after refacing; this is best accomplished while valve is tur-ning in the refacing machine.
5-62. Valve Guide Replacement. Damaged or worn valve guides are removed and new guides installed in accor Part No.
ST-62
ST-63
dance with the procedures described in the followingparagraphs.
NOTE
Unless valve guide is in obviously new condition it is bet-ter to replace it. Should the guide be bell mouthed it will be impossible to get concentric grind of the valve seat.
5-63. Valve Guide Removal. Screw the nut of valve guide
puller (ST-49) to the head of bolt (3/4-16). Place the re-tainer over valve guide inside of rocker box. Insert the bolt (3/4-16) into the retainer and valve guide. From cylinder barrel end insert the bolt (3/8-24)into the end of 3/4 inch bolt. Tighten the 3/8 bolt until snug against the valve guide. Turn the nut in rocker box in a clockwise direction until valve guide is out of cylinder head..
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