Piston, Engine
PISTON AND PISTON PIN CLEARANCEDiameter of Piston Pin Bore
^ Measure the diameter of piston pin bore using an inside micrometer.
Outer Diameter of Piston Pin
^ Measure outer diameter of piston pin using a micrometer.
Piston to Piston Pin Clearance
(Piston pin clearance) = (Piston pin bore diameter) - (Outer diameter of piston pin)
Standard: 0.002 - 0.006 mm (0.0001 - 0.0002 in)
^ If clearance exceeds specification, replace either or both of piston/piston pin assembly and connecting rod assembly with reference to specification of each parts.
^ Refer to piston selection table to replace piston/piston pin assembly.
^ Refer to connecting rod bearing selection table to replace connecting rod.
NOTE:
^ The connecting rod small end grade and piston pin hole (piston pin) grade are provided only for the parts installed at the plant. For service parts, no grades can be selected. Only 0 grade is available.
^ Refer to EM-201, "CONNECTING ROD BUSHING OIL CLEARANCE (SMALL END)" for the values for each grade at the plant. Service Limits & General Specifications
^ Regarding marks on piston head, Refer to EM-192, "HOW TO SELECT A PISTON". How to Select Piston and Bearing
PISTON TO CYLINDER BORE CLEARANCE
Inner Diameter of Cylinder Bore
^ Using a bore gauge, measure cylinder bore for wear, out-of-round and taper at 6 different points on each cylinder. (X and Y directions at A, B and C). The Y axis is in the longitudinal direction of the engine.
NOTE: When determining cylinder bore grade, measure cylinder bore at B position.
^ If the measured value rebore exceeds the limit, or if there are scratches and/or seizure on the cylinder inner wall, hone the inner wall.
^ An oversize piston is provided. When using an oversize piston, rebore the cylinder so that the clearance of the piston cylinder satisfies the standard.
Oversize (OS): 0.2 mm (0.008 in)
Outer Diameter of Piston
^ Measure piston skirt diameter using a micrometer.
^ Measure point (distance from the top): 42 mm (1.65 in)
Piston to Cylinder Bore Clearance
^ Calculate by outer diameter of piston skirt and inner diameter of cylinder (direction X, position B). (Clearance) = (Inner diameter of cylinder) - (Outer diameter of piston skirt).
Standard: 0.010 - 0.030 mm (0.0004 - 0.0012 in)
Limit: 0.08 mm (0.0031 in)
^ If it exceeds the limit, replace piston/piston pin assembly.
Reboring Cylinder Bore
1. Cylinder bore size is determined by adding piston-to-bore clearance to piston diameter "A".
Rebored size calculation: D = A + B - C
D: Bored diameter
A: Piston diameter as measured
B: Piston-to-bore clearance (standard value)
C: Honing allowance 0.02 mm (0.0008 in)
2. Install main bearing caps, and tighten to the specified torque. Otherwise, cylinder bores may be distorted in final assembly.
3. 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 in) or so in diameter at a time.
4. Hone cylinders to obtain specified piston-to-bore clearance.
5. Measure finished cylinder bore for out-of-round and taper.
^ Measurement should be done after cylinder bore cools down.
PISTON, PISTON RING, AND PISTON PIN
Available Piston
Piston Ring
Piston Pin