NMWR-9-2815-220 Overhaul Manual for M60 M88 Engine AVDS-1790-2CA, AVDS-1790-2DA, AVDS-1790-2DR Download
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NMWR 9-2815-220 CYLINDER ASSEMBLY OVERHAUL—Continued 0012 00 REPAIR – Continued (2) Cylinder bore honing. a Honing stones are used alternately around the honing head. b The hone angle should be 35 to 55 degrees to the horizontal (70° included angle). Spindle speed should be 77 rpm, with a vertical reciprocating rate of 43 cycles per minute. c The surface finish should be developed in two stages. Rough hone the entire length of the bore, using moderately heavy stone pressure, until the ring ridge is removed and the entire bore has a cross hatch pattern. Finish hone using the same stones, with very light pressure, for approximately five to eight strokes. This operation will remove rough edges and fragmented metal left from the rough hone operation. NOTE The ring ridge may be removed using short stones and a short stroking action prior to the full rough and finish hone cycle. Under no circumstances should short cycle strokes be performed after the full length strokes have been completed. d Honing oil should be principally kerosene with a sulpher based oil. Adequate filtration should be provided with both magnetic and paper filters recommended. A recommended mixture is 27 1/2 parts kerosene to 22 1/2 parts sulpher based oil. e After honing, the cylinder bore should be washed with soap and water at 160°F (71° C), dried, and a light coating of oil applied. 3. Cylinder exterior. (a) Cooling fins. Straighten bent fins as near as possible to their original spacing. Replace a cylinder assembly when more than one percent of barrel cooling fin area is broken. Also replace cylinder assembly if head fin is broken more than half the depth of the fin or more than two inches long. A cylinder assembly can be used if it has not more than three acceptable defects, or if no two of the defects are on adjacent fins. Repair damaged cylinder head fins as outlined below. (1) Blending. Use a fine mill file to remove sharp corners on broken head fins. Avoid removing more metal than necessary to produce a smoothly blended edge on the damaged fin. (2) Blended fin depth. The depth of any blended fin must not be less than 50 percent of its original depth. When blended fin is less than 50 percent of original depth, replace the cylinder assembly. (b) Studs and inserts. Refer to WP 0005 00, Table 3, and Figure 12 when replacing damaged, bent, or stripped cylinder assembly studs. Refer to WP 0005 00 when replacing damaged threaded inserts. 4. Valve rocker arm cover and associated parts. (a) Repair of the rocker arm cover by welding is permissible in the areas shown in Figure 13. Refer to WP 0005 00 for general welding instructions. 0012 00-14 Change 1