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 Piston Size Based On Cylinder Bore
Courtesy of FORD MOTOR CO.

NOTE: For precision fit, new pistons are divided into three categories (grade sizes). A paint spot on the new pistons indicates the grade size. Choose the piston with the correct paint color after measuring the cylinder bore diameter.

Choose the piston with the correct paint color.
- Refer to ENGINE- 3.8L & 3.9L or ENGINE- 4.6L (2V) or ENGINE- COBRA 4.6L (4V) or ENGINE - MACH1 4.6L (4V) for the procedure .
  
  Fig 2: Identifying Piston Paint Mark
  Courtesy of FORD MOTOR CO.