TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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proximately 4 inches long and slotted at 0.80 inch intervals 15 degrees to the horizontal to a depth of 0.12 inch from the bottom of the stone. The stones are mounted to 1 / 16 inch thick cork backing before mounting in the shell. This design allows the stone to conform to the tapered section of the bore. The stones should be mounted as per Micromatic Design No. 47415 - SA or equivalent. This number represents size 7 / 16 x 1 / 2 x 4 stones mounted with cork backing and slotted. This design will fit Micromatic stone holder No. 33960-5 and Micromatic Model 5R-SFE-8 Blind End Tool. (2) The surface finish should be devel- oped in two stages. Rough hone the entire length of the bore, using moderately heavy stone pressure, until the ring ridge is removed and entire bore has a cross hatch pattern. Finish hone using the same stones, with a very light pressure, for approximately 5 to 8 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 are short cycle strokes to be performed after the full length strokes have been completed. (3) Honing oil should be principally kerosene with a sulphurized base oil. Adequate filtration should be provided with both magnetic and paper filters recommended. A suggested oil is twenty-seven and one half (27-1 / 2) parts kerosene to twenty-two and one half (22-1 / 2 parts Stuarts’ Superkool base oil. This may be purchased from the D. A. Stuart Oil Company, 8350 Military Avenue, Detroit, Michigan 48204.) (4) The hone angle should be 35 degrees to horizontal (70 degrees included angle). Spindle speed should be 77 rpm, with a vertical reciprocating rate of 43 cycles per minute. (5) When diameter of bore at top of ring travel is more than 5.7610 inches after honing, replace cylinder. (6) Clean cylinder with a power brush and hot (160°F) soapy water. Dry thoroughly. Lubricate cylinder bore to prevent rust. e. Camshaft Bearings. Remove minor nicks, burs, or scratches from camshaft bearing sur- faces with crocus cloth dipped in dry-cleaning solvent or mineral spirits paint thinner. Replace cylinder assembly when camshaft bearing surfaces are scored, galled, or deeply pitted, or when they do not conform to limits specified in overhaul standards (table 6-15). f. Cylinder Exterior. (1) Cooling fins. Straighten bent fins as near as possible to their original spacing. Replace cylinder assembly when more than one percent of barrel cooling fin area is broken. Replace cylinder assembly if head finis 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 described in (a) through (c), below, and in TB 9-2800-207-50. (a) Use a fine mill file to remove sharp corners of broken head fins. (b) Do not remove more metal than necessary to produce a smoothly blended edge on the damaged fin. (c) 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 cylinder assembly. (2) Studs and inserts. Replace damaged, bent, or stripped studs as described in paragraph 6-4e and table 6-16. Replace defective helical- coil inserts as described in paragraph 6-5. 6-71