Inspection Of Piston And Connecting Rod Assemblies

1. CLEAN PISTON

(a) Using a gasket scraper, remove the carbon from the piston top.

(c) Using solvent and a brush, thoroughly clean the piston.

NOTICE: Do not use a wire brush.

Measuring Piston Diameter

2. INSPECT PISTON

A. Inspect piston oil clearance

HINT: There are three sizes of the standard piston diameter, marked "1", "2" and "3" accordingly. The mark is stamped on the piston top.

(a) Using a micrometer, measure the piston diameter at right angles to the piston pin center line, 23.5 mm (0.925 in.) from the piston head.

Piston diameter:

STD Mark "1" 86.911 - 86.921 mm (3.4217-3.4221 in.) Mark "2" 86.921 - 86.931 mm (3.4221 - 3.4225 in.) Mark "3" 86.931 - 86.941 mm (3.4225 - 3.4229 in.) O/S 0.50 87.411 - 87.441 mm

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Mark 2 or 3

Front Mark (Cavity)

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(b) Measure the cylinder bore diameter in the thrust directions. (See step 4 on page EM-200)

(c) Subtract the piston diameter measurement from the cylinder bore diameter measurement.

Standard oil clearance: 0.079 - 0.099 mm

Maximum oil clearance: 0.119 mm (0.0047 in.)

If the oil clearance is greater than maximum, replace all the four pistons and rebore all the four cylinders. If necessary, replace the cylinder block.

HINT (Use new cylinder block): Use a piston with the same number mark as the cylinder bore diameter marked on the cylinder block.

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Inspecting Piston Rings

B. Inspect piston ring groove clearance

Using a feeler gauge, measure the clearance between new piston ring and the wall of the piston ring groove.

Ring groove clearance: 0.030 - 0.070 mm

If the clearance is greater than maximum, replace the piston.

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C. Inspect piston ring end gap

(a) Insert the piston ring into the cylinder bore.

(b) Using a piston, push the piston ring a little beyond the bottom of the ring travel, 115 mm (4.53 in.) from the top of the cylinder block.

Sbc Oil Galley Plug DiagramOjo Llorando Dibujo

(c) Using a feeler gauge, measure the end gap.

Standard end gap:

(0.0138-0.0234 in.) Oil (Side rail) 0.200 - 0.550 mm

Maximum end gap:

If the end gap is greater than maximum, replace the piston ring. If the end gap is greater than maximum, even with a new piston ring, rebore all the four cylinders or replace the cylinder block.

D. Inspect piston pin fit

At 60°C (140°F), you should be able to push the piston pin into the piston pin hole with your thumb.

3. INSPECT CONNECTING ROD

A. Inspect connecting rod alignment

Using rod aligner and feeler gauge, check the connecting rod alignment.

Maximum bending:

If bend is greater than maximum, replace the connecting rod assembly.

Maximum twist:

If twist is greater than maximum, replace the connecting rod assembly.

B. Inspect piston pin oil clearance

(a) Using a caliper gauge, measure the inside diameter of the connecting rod bushing.

Bushing inside diameter: 22.005 - 22.017 mm

Connecting Rod Bending Check

(b) Using a micrometer, measure the piston pin diameter.

Piston pin diameter: 21.997 - 22.009 mm

(c) Subtract the piston pin diameter measurement from the bushing inside diameter measurement.

Standard oil clearance: 0.005 - 0.011 mm

Maximum oil clearance: 0.05 mm (0.0020 in.)

If the oil clearance is greater than maximum, replace the bushing. If necessary, replace the piston and piston pin as a set.

C. If necessary, replace connecting rod bushing

(a) Using SST and a press, press out the bushing. SST 09222-30010

(b) Align the oil holes of a new bushing and the connecting rod.

(c) Using SST and a press, press in the bushing. SST 09222-30010

(d) Using a pin hole grinder, hone the bushing to obtain the standard specified clearance (see step B above) between the bushing and piston pin.

(e) Check the piston pin fit at normal room temperature.

Coat the piston pin with engine oil, and push it into the connecting rod with your thumb.

D. Inspect connecting rod bolts

(a) Install the cap nut to the connecting rod bolt. Check that the cap nut can be turned easily by hand to the end of the thread.

How Measure Connecting Rods

(b) If the cap nut cannot be turned easily, measure the outside diameter of the connecting rod bolt.

Standard diameter: 7.860 - 8.000 mm

Minimum diameter: 7.60 mm (0.2992 in.)

HINT: If the location of this area cannot be judged by visual inspection, measure the outer diameter at the location shown in the illustration.

If the ouside diameter is less than minimum, replace the connecting rod bolt and cap nut as a set.

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Responses

  • Maura
    What size standard mr2 pistons?
    8 years ago

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