HOOD AS 1919110 - Caterpillar

Correct Use Of Plastigage To Measure Bearing Clearances
When tight clearances [less than .004" (0.1 mm)] are checked, the readings (indications) from the Plastigage can be .0005 to .0010" (0.013 to 0.025 mm) less than the exact clearance.
For example, an exact clearance of .003" (0.076 mm) can possibly show as only .002" (0.051 mm) when checked with Plastigage.
Recommendations For Measurement Of Main Bearing Clearances With Plastigage
IMPORTANT: Plastigage must be used correctly when bearing clearances are measured.
1. Put the bearing in the cap and saddle of the cylinder block with the tabs in the slots.2. Be sure the bore and backs of both bearing halves are clean and dry.3. Put the Plastigage at the crown (top) of the bearing half that is in the cap. The Plastigage must not be extended over the edge of the bearing.4. The crankshaft journal must not have any oil on it.5. Install the bearing cap and bolts. Use the correct torque-turn specifications and procedures. Be careful not to move the main bearings out of their seat when the cap is installed. DO NOT use an impact wrench on the journal to be measured or a journal next to the one that is to be measured. This can cause more compression of the Plastigage which will prevent a correct indication.6. DO NOT turn the crankshaft. When repairs are made to an engine in a chassis or an engine in a normal vertical position, the crankshaft must be lifted against the top of the upper bearing and held there until the clearance is measured. If the crankshaft is not lifted and held, the weight of the crankshaft will change the main bearing clearance reading. To prevent this, use a jack under the crankshaft counterweight next to the bearing which is to be measured.If the engine is on its side in an engine stand, the crankshaft must be tight against the top of the bearing in the cylinder block saddle. This will prevent distortion of the Plastigage. When the engine is out of the chassis, put the block so the crankshaft bores are up. In this position, crankshaft support is not necessary.
7. Remove the cap, but DO NOT remove the Plastigage before it is measured. The Plastigage can be on the cap, on the bearing, or on both.8. Carefully measure the compression of the Plastigage with the correct scale, inches or millimeters, on the Plastigage package. Write down the measurements.The wider the compression, the smaller the clearance.
Many times, Plastigage shows a compression area with variable thickness and some twists and bends. Know the thickness specifications for the clearance and use the gauge on the Plastigage package to check if the major areas of the compression are inside the tolerances for the clearance.
With new bearings, the clearances must be near the lowest end of the specifications. The Plastigage will show smaller than exact clearances in this type of measurement.
9. Remove the Plastigage. Before the cap is installed, put oil on the crankshaft journal. Then install the cap and