How To Do Just About Everything
By torque63
Made from a special extruded plastic thread with accurately controlled crush properties, Plastigage provides a fast and accurate way to check bearing clearances.
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Ever wonder how bearing clearances inside an engine are measured? I will show you how easily this is done.
If you are going to measure a crankshaft, assemble the engine together with the crankshaft installed with the new bearing inserts in the block and main caps. Make sure all the caps are numbered, in order and installed properly with the arrows pointing forward. All fasteners/bolts will need to be torqued to specification.
Loosen the bolts of the bearing cap that you want to check clearance on. Remove the bolts and the cap. Wipe assembly oil off of the surface of the crankshaft where you want to check for clearance, use a clean lint free paper towel or cloth.
Tear off a piece of plastigage. You will need to open the paper to remove the plastigage, place the plastigage across the surface of crankshaft. Try to position the plastigage in the center of the journal surface. Install the bearing cap and torque bolts to specification, remove the bolts and the bearing cap. You will see the crushed plastigage on the journal.
Using the paper that came with the plastigage, use the scale on the side of the wrapper to measure the crushed plastigage. Compare your measurement to the clearance specification, if you are within range then you are ok to assemble. If the measurement falls between two sizes then you can estimate what the size in between is.
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