TM 5-3825-226-24BASIC BLOCKCYLINDER BLOCK HONINGThe following preliminary check is essential todetermine if honing is necessary, and if so, the size tohone.Measure all cylinder bores during disassemblyusing the 1P3537 Bore Gauging Group. This groupincludes a 1P3535 Dial Bore Gauge Group and a1P3536 Size Setting Fixture Group. The bore gauginggroup provides more accurate measurements than othermethods, such as inside micrometers. When setting thegauge, always be sure the gauge pin has sufficienttravel to measure the points of maximum wear in thebore. In a cylinder bore, maximum wear is usuallyacross the diameter perpendicular to the crankshaftcenterline, either at the top or bottom of ring travel.Normal wear usually will not exceed .020 in. (0.51 mm);however, if bore wear is greater than .020 in. (0.51mm), hone the block .040 in. (1.02 mm) oversize. Thefact that the block can be honed both .020 in. (0.51mm) and .040 in. (1.02 mm) oversize will allow a blockto be reconditioned twice under normal wear conditions.The standard bore size is 4.5000 to 4.5015 in. (114.300to 114.338 mm).1P3537 BORE GAUGING GROUPWhen reconditioning an engine, the bore size isthe determining factor as to the necessity of honing thebores. If bores are worn .006 in. (0.15 mm) more thanthe standard size, the block should be honed. However,additional service may be obtained without honing ifwear does not exceed the maximum wear limit of .0085in. (0.216 mm)Before honing, inspect the bottom of eachcylinder bore adjacent to the main bearing saddle orweb. Some of the saddles may overlap the edge ofcylinder bores enough to interfere with honing. Whereoverlap exists, machine a relief in the saddle to provideclearance for the honing tool. The radius of the reliefmust be concentric with the cylinder bore and .030 ±.005 in. (0.76 ± 0.13 mm) larger than the bore radius.The relief extends .62 in. (15.7 mm) beyond the bottomof the bore, as shown. This provides adequateclearance for honing.RELIEF IN SADDLES and CHAMFER AFTERHONINGWhen honing, check bore size at severallocations in the length of the bore and around thecircumference. Specifically measure at pointsperpendicular to the crankshaft centerline at locations.25 in. (6.4 mm) from each end and at center of bore.These three specific locations are primary gauge pointsduring and after honing.PRIMARY GAUGING POINTS3-365
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