Boring Procedure
Important:
| • | The coating on the piston allows for an interference fit between the cylinder and the bore. The piston diameter can NOT be measured accurately because the piston coating is not a consistent thickness. Do NOT measure the piston diameter. |
| | To select the correct piston for installation, the cylinder bore must be measured. If the cylinder bore diameter is within service specifications, install the original piston/connecting rod assembly or a new, standard size piston/connecting rod assembly.
A piston/connecting rod assembly may be used again if, after cleaning and inspection, the piston is not damaged. If the cylinder bore is NOT within specifications, the cylinder must be resized to accept a new, oversized piston. |
| • | If you do not inspect the cylinder block, the boring bar may be tilted. This may result in incorrect rebored cylinder wall to crankshaft angle. |
- Before you use any type of boring bar, clean the top of the cylinder block in order to remove any dirt or burrs.
- Carefully follow the instructions furnished by the manufacturer regarding use of equipment.
- When you rebore cylinders, ensure all crankshaft bearing caps are in place.
| • | Tighten the bearing caps to the proper torque in order to avoid distortion of the bores in the final assembly. |
| • | The crankshaft must be removed prior to cylinder boring. |
- When you take the final cut with a boring bar, leave 0.03 mm (0.001 in) on the diameter for finish honing. This gives the required position to the cylinder clearance specifications. Carefully perform the honing and boring operation
in order to maintain the specified clearances between pistons, rings, and cylinder bores.
Honing Procedure
Important: Always remove all bearings and components from the engine block before cleaning, boring, or honing the engine block.
- When honing the cylinders, follow the manufacturers recommendations for equipment use, cleaning, and lubrication.
| • | Use only clean, sharp stones of the proper grade for the amount of material you remove. |
| • | Dull, dirty stones cut unevenly and generate excessive heat. |
| • | Do not hone to a final grade with a coarse or medium-grade stone. |
| • | Leave sufficient metal so that all stone marks may be removed with fine grade stones. |
| • | The rehoned surface finish should be 0.25-0.50 micrometer (10-20 microinch). |
| • | Perform final honing with a fine-grade stone and hone the cylinder in a cross-hatch pattern at 20 to 30 degrees to obtain the proper clearance. |
- During the honing operation, thoroughly clean the cylinder bore.
| • | Repeatedly inspect the cylinder bore for fit with the selected oversized piston. |
| • | All measurements of the cylinder bore should be made with the components at normal room temperature. |
- To eliminate taper in the cylinder when honing, make full strokes of the hone in the cylinder. Repeatedly inspect the measurement at the top, the middle, and the bottom of the bore.
| • | The finish marks should be clean but not sharp. |
| • | The finish marks should be free from embedded particles and torn or folded metal. |
- When finished, the reconditioned cylinder bores should have less than or meet the specified out-of-round or taper requirements.
- After final honing and before the piston is inspected for fit, clean the bores with hot water and detergent.
| 5.1. | Scrub the bores with a stiff bristle brush and rinse the bores thoroughly with hot water. Do not allow any abrasive material to remain in the cylinder bores. |
| • | Abrasive material may cause premature wear of new piston rings and cylinder bores. |
| • | Abrasive material will contaminate the engine oil and may cause premature wear of the bearings. |
| 5.2. | After washing the cylinder bore, dry the bore with a clean shop towel. |
- Perform final measurements of the cylinder bore.
- Permanently mark the piston for the specific cylinder to which it has been fitted.
- Apply clean engine oil to each cylinder bore in order to prevent rusting.
