TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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CHAPTER 7 ASSEMBLY OF ENGINE Section I. GENERAL 7-1. Cleanliness The engine is a precision product and extreme care and cleanliness must be exercised in all phases of assembly operations to insure satisfactory engine performance. Dirt and dust, even in minute quantities, are abrasive. After cleaning and just before assembly, coat all bearings, shafts, and contact surfaces with engine oil (OE). This will insure sufficient lubrication of moving parts when first put into operation. 7-2. General Assembly Instructions a. Gaskets. Always use new gaskets when assembling the engine. Use new preformed packings and annular copper gaskets throughout engine assembly. An engine overhaul parts kit 2815-678-4245, consisting of all necessary gaskets and preformed packings, is available for use during engine overhaul. b. Kits and Sets. Several of the components of the engine are available in kits or sets. Whenever a kit or set is used for parts replacement, all components of the kit or set should be installed, except for the auxiliary oil filter parts kit, FSN 2940-884-4801. This kit is the universal type. Refer to Appendix for specific information. c. Attaching Parts. When torque tightening nuts, bolts, and screws, and a torque specification is not noted in the text or illustration covering the installation, it is un- derstood that the standard torque values in paragraph 6-7 prevail. Whenever a nut, bolt, or screw requires that special attention be given, the torque value will be noted in the text or illustration pertaining to that operation. Torque wrench readings are of no value, unless properly used. It must be understood that it is not the force necessary to turn the nut, bolt, or screw that is important, but the resultant pull on the part that completes the union. Therefore, resistance of the nut to turning must be kept to a minimum. Threads must be clean and un- damaged, and lubricated with antiseize com- pound FSN 9150-663-1770 to reduce the friction. Note. When using a torque wrench, the final reading must be taken while the nut, cap screw, or bolt is turning. When torque reading is close to that specified when wrench is at the end of its swing, back off the nut slightly and change wrench position; then pull to the desired reading while the nut is turning. To start a partially tightened nut will require a much higher torque than that required to keep a nut turning. The ratio of pounds-torque to pounds-pull on a bolt is not an even ratio and excess torque may easily overstress the bolt. Under-torquing bolts and studs subject to cyclic loads such as cylinder base studs and connecting rod bolts will result in fatigue failures. It is therefore important that the torque values specified in this manual be followed to avoid failures of fasteners. Note. Do not exceed torque specified. d. Lock Nuts, Tab Washers, Locking Wire, Lock Washers, and Cotter Pins. All bolts and nuts should be secured with lock nuts, tab washers, locking wire, lockwashers, or cotter pins, as specified. Many engine failures have been traced to neglect of this simple precaution. 7-3. Installation Instructions Note. References to figures in this Chapter are listed in the reverse order of disassembly both in text and tables, which is the sequence required to accomplish reassembly of the engine; i.e., 5- 24 through 5-11. Usually the step-by-step procedure to be followed for installing subassemblies on the engine are given immediately following the removal procedure in Chapter 5. This method of installation will be used throughout this chapter unless otherwise indicated in the contents table immediately following each paragraph. Each contents table lists engine components, grouped in proper assembly order, and the appropriate paragraph reference and / or figure reference for installation procedures. 7-1