1 . Refer to “Specifications” for tolerances. 2 . Set the gage so the thrust pin must be forced in about 7 mm (0.250 in.) to enter the gage in the cylinder bore. 3 . Center the gage in the cylinder and turn the dial to “0”. 4 . Carefully work the gage up and down to determine taper and turn it to different points around the cylinder wall to determine the out-of- round condition. Measure the bore both parallel to and at right angles to the engine centerline. Measure at the top, middle, and bottom of the bore and note the readings. 5 . Recondition the cylinder bore as necessary, as outlined later. Figure 12-27 Typical Cylinder Wear Pattern Figure 12-28 Measuring Cylinder Bore Gage 3 .
If the cylinders are found to exceed the specified out-of-round or taper, honing or boring will be necessary. Any cylinders that were found to have less than 0.13 mm (0.005 in.) wear or taper may not entirely clean up when fitted to a high limit piston. If it is desired to entirely clean up the bore in these cases, it will be necessary to rebore for an oversize piston. If more than 0.13 mm (0.005 in.) taper or wear, they should be bored and honed to the smallest oversize that will permit complete resurfacing of all cylinders. 4 . Fine vertical scratches made by ring ends will not, by themselves, cause excessive oil consumption; therefore, honing to remove them is unnecessary. 5 .
Make sure the honing stones are clean, sharp, and straight. Move the hone up and down to produce a 45° to 65° cross-hatch pattern. Clean the bore thoroughly with soap and water. Dry and rub in clean engine oil, then remeasure. 6 . If honing is not required, the cylinder bores should be cleaned with a hot water and detergent wash. Apply clean engine oil to the bore after cleaning. Figure 12-26 Checking the Cylinder Bore Cylinder Bore Reconditioning Figures 12-27 and 12-28 1 . Measure the cylinder bore for out of round and taper as outlined previously. 2 . Measure for wear at the top of the bore (point “A”) and at the bottom (point “B”).
• Cylinder bores can be measured by setting the cylinder gage dial at zero in the cylinder at the point of desired measurement. Lock the dial indicator at zero before removing from the cylinder, and measure across the gage contact points with an outside micrometer, with the gage at the same zero setting when removed from the cylinder (figure 12- 28). G643 (E) Service Manual Chapter 3. Engine Mechanical System 74