Isuzu KB P190. Manual - part 223

ENGINE MECHANICAL   6A – 87 

 

 

 

3.  Use a feeler gauge to measure the piston ring gap. 

If the measured value exceeds the specified limit, the 
piston ring must be replaced. 

 

 

Piston Ring Gap 

mm (in)

4JA1T (L), 4JA1TC 

 Standard 

 

Limit 

1st Compression Ring

2nd Compression Ring

0.3-0.3 

(0.0118-0.0197) 

Oil Ring 

0.250-0.450 

(0.0098-0.0177) 

1.5 

(0.059) 

 

 

4JH1TC 

 Standard 

 

Limit 

1st Compression Ring

2nd Compression Ring

0.3-0.5 

(0.0118-0.0197) 

Oil Ring 

0.250-0.450 

(0.0098-0.0177) 

1.5 

(0.059) 

 

 

 

 

 

Piston Ring and Piston Ring Groove Clearance 

Use a feeler gauge to measure the clearance between the 
piston ring and the piston ring groove at several points around 
the piston. 

If the clearance between the piston ring and the piston ring 
groove exceeds the specified limit, the piston ring must be 
replaced. 

 

 

Piston Ring and Piston Ring Groove Clearance 

mm (in)

4JA1T (L), 4JA1TC 

 Standard 

 

Limit 

1st Compression Ring

0.09-0.125 

(0.0035-0.0049) 

2nd Compression Ring

0.05-0.085 

(0.0020-0.0033) 

Oil Ring 

0.03-0.070 

(0.0012-0.0028) 

0.15 

(0.0059) 

 

 

4JH1TC 

 Standard 

 

Limit 

1st Compression Ring

0.09-0.130 

(0.0035-0.0051) 

2nd Compression Ring

0.05-0.090 

(0.0020-0.0035) 

Oil Ring 

0.03-0.070 

(0.0012-0.0028) 

0.15 

(0.0059) 

 

 

 

015RY00021

015LX025

6A – 88  ENGINE MECHANICAL 

 

 

 

 

4.  Visually inspect the piston rings. 

If a piston ring groove is damaged or distorted, the piston 
must be replaced. 

 

 

 

 

 

Piston Pin Diameter 

Use a micrometer to measure the piston pin diameter at 
several points. 

If the measured value is less than the specified limit, the piston 
pin must be replaced. 

 

 

Piston Pin Diameter 

 mm 

(in)

Standard  

Limit 

30.995-31.000 

(1.2202-1.2204) 

30.97 

(1.2193) 

 

 

 

 

 

Piston Pin and Piston Clearance 

Use and inside dial indicator to measure the piston pin hole (in 
the piston). 

 

 

Piston Pin Hole

 mm 

(in)

4JA1T (L) 

31.002-31.010 (1.2206-1.2208) 

4JA1TC, 4JH1TC

31.005-31.013 (1.2207-1.2210) 

 

 

Piston Pin and Piston Pin Hole Clearance 

mm (in)

4JA1T (L) 

0.002-0.015 (0.00008-0.0006) 

4JA1TC, 4JH1TC

0.005-0.018 (0.0002-0.0007) 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CYLINDER HEAD GASKET SELECTION 

Cylinder head gasket is determined by the piston head 
projection from the cylinder body upper surface, in order to 
improve engine performance. 

Three types of gasket are provided by the difference of 
thickness. Select the adequet one out of three grades of 
gasket, according to the following procedure. 

Before measurement, clear off carbon from the piston head 
and cylinder body surface and also clean the place where a 
gasket was installed. 

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011LX011

ENGINE MECHANICAL   6A – 89 

 

  

 

RTW36ASH001701 

Piston Head Projection Measuring Point 

1.  Use a dial indicator to measure the piston projection 

amount. 

2.  Refer to the illustration for the piston head projection 

measuring positions. 

All measuring positions should be as close as possible to 
the cylinder liner. 

 

 

 

 

 

 

3.  Measure the points 1, 2, 3, 4 and obtain two differences 1-

2 and 3-4 on each cylinder. 

Calculate the average value of the piston head projection 
on each cylinder. 

4.  Obtain the maximum value in the four cylinders. 

5.  Determine the gasket grade required to the maximum 

value described above in accordance with the following 
table. 

 

 

 

 

Cylinder Head Gasket Combination 

mm (in)

 

Cylinder Head Gasket Combination 

4JA1T (L), 4JA1TC 

mm (in)

Gasket Grade Mark Piston Projection 

Gasket Thickness

(Reference) 

A 

0.718-0.773 

(0.0283-0.0304) 

1.6 

(0.0630) 

B 

0.773-0.819 

(0.0304-0.0322) 

1.65 

(0.0650) 

C 

0.819-0.874 

(0.0322-0.0344) 

1.70 

(0.0669) 

 

 

4JH1TC mm 

(in)

Gasket Grade Mark Piston Projection 

Gasket Thickness

(Reference) 

A 

0.215-0.265 

(0.0085-0.0104) 

1.3 

(0.5118) 

B 

0.265-0.315 

(0.0104-0.0124) 

1.35 

(0.5315) 

C 

0.315-0.365 

(0.0124-0.0144) 

1.4 

(0.5512) 

NOTE: 
Difference of the each piston projection and must be 
equal or within 0.1 mm (0.004 in). 

 

 

 

011RY00027

011RY00030

6A – 90  ENGINE MECHANICAL 

 

 

 

 

 

 

 

 

CONNECTING ROD 

Connecting Rod Alignment 

Use a connecting rod aligner to measure the distortion and the 
parallelism between the connecting rod big end hole and the 
connecting rod small end hole. 

If either the measured distortion or parallelism exceed the 
specified limit, the connecting rod must be replaced. 

 

 

Connecting Rod Alignment Per Length of 100 mm (3.94 in) 

mm (in)

 Standard 

Limit 

Distortion 

0.08 (0.003) or Less 

0.20 (0.008) 

Parallelism 

0.05 (0.002) or Less 

0.15 (0.006) 

 

 

 

 

 

Connecting Rod Side Face Clearance 

1.  Install the connecting rod to the crankpin. 

2.  Use a feeler gauge to measure the clearance between the 

connecting rod big end side face and the crankpin side 
face. 

If the measured value exceeds the specified limit, the 
connecting rod must be replaced. 

 

 

Connecting Rod Big End and Crankpin Side Face Clearance

mm (in)

Standard  

Limit 

0.23 (0.009) 

0.35 (0.014) 

 

 

 

 

 

Piston Pin and Connecting Rod Small End 
Bushing Clearance 

Use a caliper calibrator and a dial indicator to measure the 
piston pin and connecting rod small end bushing clearance. 

If the clearance between the piston pin and the connecting rod 
small end bushing exceeds the specified limit, replace the 
piston pin and/or the connecting rod. 

 

 

Piston Pin and Connecting Rod Small End 
Bushing Clearance  

mm (in)

 Standard 

  Limit 

4JA1T (L) 

0.008-0.020 

(0.003-0.0008) 

0.050 (0.002) 

4JA1TC, 

4JH1TC 

0.005-0.018 

(0.0002-0.0007) 

0.050 (0.002) 

 

 

 

015LX034

011RY00029

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