Piston Selection

NOTE: The cylinder bore must be within the specifications for taper and out-of-round before fitting a piston.

Select a piston size based on the cylinder bore.

Fig 1: Identifying Cylinder Bore Measuring Directions
Courtesy of FORD MOTOR CO.

NOTE: For precision fit, new pistons are divided into 3 categories within each size range based on their relative position within the range. A paint spot or specific size grade on a new piston indicates the position within the size range.

Choose the piston with the correct paint color or specific size grade.
- Refer to the SPECIFICATIONS for 3.5L & SPECIFICATIONS for 3.5L GDTI for the procedure.
  
  Fig 2: Location of Paint Spot Or Specific Size Grade On Piston
  Courtesy of FORD MOTOR CO.