Block and Piston Inspection
Block and Piston Inspection1. Remove the crankshaft and pistons.
2. Check the piston for distortion or cracks.
3. Measure the piston diameter at a point 11 mm (0.4 inch) from the bottom of the skirt. There are two standard-size pistons (No Letter or A, and B). The letter is stamped on the top of the piston. Letters are also stamped on the block as cylinder bore sizes.
Piston Diameter:
Standard (New):
No Letter (or A): 85.980 - 85.990 mm (3.3850 - 3.3854 inch)
B: 85.970 - 85.980 mm (3.3846 - 3.3850 inch)
Service Limit:
No Letter (or A): 85.930 mm (3.3831 inch)
B: 85.920 mm (3.3827 inch)
Oversize Piston Diameter: 0.25: 86.230 - 86.240 mm (3.3949 - 3.3953 inch)
4. Measure wear and taper in direction X and Y at three levels in each cylinder as shown. If measurements in any cylinder are beyond the Oversize Bore Service Limit, replace the block. If the block is to be rebored, refer to step 7 after reboring.
Cylinder Bore Size:
Standard (New): A or I: 86.010 - 86.020 mm (3.3862 - 3.3866 inch)
B or II: 86.000-86.010 mm (3.3858 - 3.3862 inch)
Service Limit: 86.070 mm (3.3886 inch)
Oversize: 0.25: 86.250 - 86.260 mm (3.3957 - 3.3961 inch)
Reboring limit: 0.25 mm (0.01 inch) maximum
Bore Taper:
Limit: (Difference between first and third measurement) 0.05 mm (0.002 inch)
5. Scored or scratched cylinder bores must be honed.
6. Check the top of the block for warpage. Measure along the edges and across the center as shown.
Engine Block Warpage:
Standard (New): 0.07 mm (0.003 inch) maximum
Service Limit: 0.10 mm (0.O04 inch)
7. Calculate the difference between the cylinder bore diameter and the piston diameter. If the clearance is near or exceeds the service limit, inspect the piston and cylinder block for excessive wear.
Piston-to-Cylinder Clearance:
Standard (New): 0.020 - 0.040 mm (0.0008 - 0.0016 inch)
Service Limit: 0.05 mm (0.002 inch)
Cylinder Honing
Only a scored or scratched cylinder bore must be honed.
1. Measure the cylinder bores. If the block is to be reused, hone the cylinders and remeasure the bores.
2. Hone the cylinder bores with honing oil and a fine (400 grit) stone in a 60 degree cross-hatch pattern (A). Use only a rigid hone with 400 grit or finer stone such as Sunnen, Ammco, or equivalent. Do not use stones that are worn or broken.
3. When honing is complete, thoroughly clean the engine block of all metal particles. Wash the cylinder bores with hot soapy water, then dry and oil them immediately to prevent rusting. Never use solvent, it will only redistribute the grit on the cylinder walls.
4. If scoring or scratches are still present in the cylinder bores after honing to the service limit, rebore the cylinder block. Some light vertical scoring and scratching is acceptable if it is not deep enough to catch your fingernail and does not run the full length of the bore.