Cylinder Boring and Honing
- Tools Required- J 8087 Cylinder Bore Gauge, Or Equivalent
1. Determine if any cylinders will require honing.
2. In order to identify fine vertical scratches, use a finger napkin in order to feel the scratches. You should not be able to feel a fine vertical scratch. Fine vertical scratches will not by themselves cause excessive oil consumption. Therefore, honing in order to remove fine vertical scratches is not necessary.
3. If the bore has polished areas through the hone marks but is serviceable, break the polished surface lightly with a finish hone and Install new rings.
4. Prepare the cylinder bores for reuse by cleaning them with hot water and detergent wash. Apply clean engine oil to the bore after cleaning.
NOTE:
- There is only one production standard piston grade size. When using production standard grade size pistons in all eight cylinder bores, a J is metal stamped in a single place on the cylinder block oil pan rail.
- A 0.13 mm oversize production piston is available for in a plant rework of cylinders that do not meet the production standard: specification. An S metal stamped on the pan rail next to any reworked cylinder identifies, that cylinder as production oversize. A J will also be metal stamped in a single place on the oil pan rail to represent that all remaining cylinders are production standard.
- All service oversize pistons are of the same weight as the production pistons. Using service oversized pistons will not affect engine balance.
5. Before the honing or reboring operation is started, measure all new pistons.
6. Select the smallest piston for the first fitting. The slight variation usually found between pistons in a set may provide for correction in case the first cylinder is bored too large.
7. Before using any type of boring bar, file the top of the cylinder block in order to remove any dirt or burrs. If not checked, the boring bar may be tilted which would result in the rebored cylinder wail not being at right angles to the crankshaft.
NOTE: Carefully follow the instructions furnished by the manufacture of the equipment being used.
8. When reboring cylinders, all crankshaft bearing caps must be in place and tightened to the proper torque in order to avoid distortion of the bores in the final assembly.
9. When taking the final cut with a boring bar, leave 0.03 mm (0.001 inch) on the diameter for finish honing in order to give the required position to the cylinder clearance specifications.
Perform the honing or boring operation carefully so that the specified clearance between pistons, rings, and the cylinder bores is maintained.
10. When honing the cylinders, follow the hone manufacturer's recommendations for use, cleaning, and lubrication during honing. Use only clean, sharp stones of the proper grade for the amount of material to be removed. Dull, dirty stones cut unevenly and generate excessive heat. When using coarse or medium grade stones, use care to leave sufficient metal so that all stone marks may be removed with the fine stones used for finishing to provide proper clearance.
11. Occasionally, during the honing operation, thoroughly clean the cylinder bore and check the piston selected for the individual cylinder for correct fit.
12. When honing to eliminate taper In the cylinder, make full strokes of the hone in the cylinder. Check the measurement at the top, the middle, and the bottom of the bore repeatedly.
13. Handle the pistons with care. Do not attempt to force them through the cylinder until the cylinder has been honed to the correct size. The piston can be easily distorted through careless handling.
14. When finish honing a cylinder bore to fit a piston, move the hone up and down at a sufficient speed in order to obtain very fine uniform surface finish marks in a cross-hatch pattern at the specified angle (45-65°).
15. The finish marks should meet the following requirements:
- Clean but not sharp
- Free from imbedded particles
- Free from torn or folded metal
NOTE: Measure the block and the piston at normal room temperature.
16. Determine the finish hone cylinder measurement by adding the average of the clearance specification to the measurement of the piston.
NOTE: True up refinished cylinder bores to have less than the specified out-of-round or taper.
17. Final hone each bore in order to remove all stone or cutter marks and to provide a smooth surface.
NOTE: If any of the abrasive material is allowed to remain in the cylinder bores, it will wear the new rings cylinder bores, and bearings lubricated by the contaminated oil.
18. After final honing and before the piston is checked for fit, clean the bores with hot water and detergent. Scrub with a stiff bristle brush. Rinse thoroughly with hot water.
19. After washing, brush clean the dry bore with a power-driven fiber brush.
20. Permanently mark the piston for the cylinder to which it has been fitted.
21. Apply clean engine oil to each bore in order to prevent rusting.
22. The following are the surface roughness specifications for cylinder bores:
- RA (Minimum) = 0.40 Micro-meter (16 Micro-inch)
- RA (Maximum) = 0.90 Micro-meter (32 Micro-inch)
23. Inspect the cylinder bores for scoring and other damage.
24. If one or more cylinder bores are rough, scored or worn beyond limits, smooth or true up such bores in order to fit new pistons.
25. No attempt should be made to cut down oversize pistons to fit cylinder bores as this will destroy the surface treatment and affect the weight. Use the smallest possible oversize pistons. Hone the cylinder bores to size for the proper clearances.
26. Check the cylinders for out-of-round and taper using the following procedure:
a. Refer Specifications for cylinder bore tolerances.
b. Depress the plunger on the tool 7 mm (0.03 inch) or until the tool enters the cylinder bore.
c. Center the gauge in the cylinder and turn the dial to 0.
d. Carefully work the gauge up and down the cylinder in order to determine taper. Turn the gauge to different points around the cylinder wall in order 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 the bottom of the bore. Note the readings.
e. Recondition the cylinder bore as necessary. If the bore out-of-round or taper measurements exceed 0.02 mm (0.0008 inch), it will be necessary to rebore and hone such bores and fit new pistons and rings.