Piston Selection

WARNING: This page is about a different car, the 2009 Mercury Mountaineer, 2009 Ford Explorer Sport Trac, and 2009 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

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 appropriate ENGINE - 4.0L SOHC or ENGINE - 4.6L (3V) .

Fig 2: Identifying Piston Grade Size

Courtesy of FORD MOTOR CO.