Piston Protrusion Check

For information on Ford Color Coded Illustrations, refer to OEM COLOR CODING

Special Tool(s) / General Equipment 

Check 

1. Verify that the cylinder block deck surface and the pistons are clean.
2. The piston protrusion is measured in-line front and rear avoiding raised or etched marking.

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3. NOTE: Use a commercially available deck bridge such as the Proform® 66797 Magnetic Deck Bridge or equivalent.
   • Using the dial indicator and a commercially available deck bridge, position at one of the points on the cylinder block deck surface.. Use the General Equipment: Dial Indicator
   • Zero the dial indictor on the cylinder block deck surface.

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4. NOTE: Only rotate the crankshaft clockwise.
   NOTE: The piston must remain at TDC or an inconsistent reading will result.
   • Position the dial indicator and a commercially available deck bridge, over the piston.. Use the General Equipment: Dial Indicator
   • Rotate the crankshaft until the piston is at TDC.. Use the General Equipment: Dial Indicator
   • Record the reading.

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5. • Move the dial indicator and the commercially available deck bridge, on the cylinder block deck surface at the opposite position.. Use the General Equipment: Dial Indicator
   • Zero the dial indictor on the cylinder block deck surface.

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6. • Move the dial indicator and the commercially available deck bridge, onto the piston at the opposite position.. Use the General Equipment: Dial Indicator
   • Record the reading.

   Courtesy of FORD MOTOR COMPANY

7. Average the readings and record. If the average is lower than specification, the piston is lower in the bore than it should be. This indicates a bent or twisted connecting rod.
8. Repeat on the remaining pistons.
9. Compare with the piston protrusion specification, replace any connecting rods out of specification. Refer to: Specifications .