Piston-To-Bore Clearance
PISTON-TO-BORE CLEARANCE
1. Using a bore gauge, measure cylinder bore for wear, out-of round and taper.
Standard inner diameter: ............86.000 - 86.030 mm (3.3858 - 3.3870 inch)
Wear limit: ..............0.20 mm (0.0079 inch)
Out-of-round (X - Y) standard: ............0.015 mm (0.0006 inch)
Taper (A - B and A - C) standard: .........0.010 mm (0.0004 inch)
If it exceeds the limit, rebore all cylinders. Replace cylinder block if necessary.
2. Check for score and seizure. If seizure is found, hone it.
If cylinder block and piston are replaced, match piston grade with grade number on cylinder block upper surface.
3. Measure piston skirt diameter.
Piston diameter "A": Refer to Engine; Specifications; Mechanical.
Mechanical Specifications
Measuring point "a" (Distance from the top):..........45.0 mm (1.772 inch)
4. Check that piston-to-bore clearance is within specification.
Piston-to-bore clearance = bore measurement "C" - Piston diameter "A": 0.010 - 0.030 mm (0.0004 - 0.0012 inch)
5. Determine piston oversize according to amount of cylinder wear.
Oversize pistons are available for service. Refer to Engine; Specifications; Mechanical.
Mechanical Specifications
6. Cylinder bore size is determined by adding piston-to-bore clearance to piston diameter "A".
Rebored size calculation:
D = A + B - C where,
D......Bored diameter
A......Piston diameter as measured
B......Piston-to-bore clearance
C......Honing allowance 0.02 mm (0.0008 inch)
7. Install main bearing caps and tighten to the specified torque. This will prevent distortion of cylinder bores, otherwise cylinder bores may be distorted in final assembly.
8. Cut cylinder bores.
When any cylinder needs boring, all other cylinders must also be bored.
Do not cut too much out of cylinder bore at a time. Cut only 0.05 mm (0.0020 inch) or so at a time.
9. Hone cylinders to obtain specified piston-to-bore clearance.
10. Measure finished cylinder bore for out-of-round and taper.
Measurement should be done after cylinder bore cools down.