Plastigage is a simple and cost-effective method for measuring the clearance (separation) between fitted or hidden surfaces in engine bearings, Here's how it works.
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Prepare the surfaces:
- First, separate the surfaces between which you want to measure the clearance
- Ensure that the surfaces are clean before using Plastigage. -
Apply Plastigage:
- Cut a piece of Plastigage to fit across the bearing journal (the contact surface).
- Place the Plastigage on top of the journal. -
Torque Down:
- Install the bearing cap (or rod cap) and torque it down to the specified value and angle.
- The Plastigage will be compressed between the bearing and the journal. -
Check Clearance:
- Remove the bearing cap and compare the flattened Plastigage with the scale on the Plastigage packaging.
- The width of the flattened Plastigage corresponds to the clearance.
- Use the calibrated scale to determine the actual clearance. You can interpolate between scale marks for greater accuracy. -
Repeat for Other Bearings:
- Repeat the process for other bearings in the engine.
Advantage of Plastigage:
- Inexpensive compared to bore micrometers.
- Useful for measuring clearances in split bearings or where feeler gauges cannot be inserted.
Remember to follow the specific procedures for your engine and refer to the manufacturer's specifications.