VALVE GUIDE REPLACEMENT TOOLS
GAGE SIZE REAMER
Valve Guide Hole in Cylinder (.5913/.5923 Hole)
64571 Standard 64507 .005 oversize 64678-2 64509 .010 oversize 64678-3 64511 .020 oversize 64678-4 64639 .030 oversize 64678-5
(.6613/.6623 Hole)
64940 Standard 64924 64928 .005 oversize 64924-1 64929 .010 oversize 64924-2 64930 .020 oversize 64924-3 64931 .030 oversize 64924-4
Valve Guide ID
64514 All Intake Valve 64684 64927 .4985/.4995 (Ni-Resist) Exhaust
Pilot Diameter
.4778/.4783 ST-113-2
Replacement fixture 64714 Installation drift (intake) ST-304 Installation drift (exhaust) ST-303 Valve guide puller ST-49
5-66. If it has been determined that the next oversize guide is required, select the appropriate reamer (See Table 5-2) and proceed as follows. Mount the reamer in the drill press spindle and ream the valve guide hole in the cylinder head. Check the reamed hole with the corresponding gage (See Table 5-2).
5-67. Heat the cylinder to 400 to 425°F. for a minimum of one hour. Place the new valve guide, that has been chilled, on the appropriate valve guide installation drift (See Table 5-2) and insert the guide in the hole in the cylinder head. Drive the valve guide until the drive bottoms on the lower valve spring pocket. Use driver (ST-303) for exhaust valve guide and (ST-304) for intake valve guide. Check the valve guide drive height which is measured from the lower valve spring pocket to the top of the valve guide. The dimension is .775 for exhaust valve guide and .715 for in-take valve guide. The dimension must be held within
±.010 of the above. Do not measure from the counterbore flange seat.
5-68. Any nitrided cylinder barrel that exceeds the allowable service limits in diameter, taper, or out-of-roundness must either be rebarreled or reconditioned by chrome-plating. Consult Service Instruction No. 1047 for information relative to reconditioning nitrided cylinder barrels.
5-10
ACCEPTABLE
INTAKE VALVE EXHAUST VALVE
DESIRED (1° MAX. ANGLE)
INTAKE VALVE EXHAUST VALVE
1 MAX. MAX.
NOT ACCEPTABLE INTAKE VALVE EXHAUST VALVE
SATISFACTORY SEATING
Figure 5-13. Acceptable, Desired and Non-Acceptable
Valve Contact with Seat Face
5-69. Reconditioning Chrome Plated Barrels. Although it is not practical to remove wear steps by regrinding, such barrels can be restored by a stripping and replating pro-cess. Consult Service Letter No. 159 for facilities approv-ed by Lycoming to perform this chrome plating pro-cess. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：莱康明发动机大修手册 OVERHAUL MANUAL LYCOMING 76 SERIES AIRCRAFT ENGINES(25)
