Piston Fitting
The pistons are "select fit" to achieve proper oil clearance. Engine block cylinder bore diameter grade markings (1) are stamped into the left side of the engine block. These marks are read from left to right, corresponding with cylinder number 1, 2, 3, 4, 5, 6.
Engine block cylinder bore diameter grade markings correspond to specific cylinder bore diameters. The chart below identifies the two engine block grade markings and their associated cylinder bore diameters.
| Engine Block Marking | Cylinder Bore Size mm (in.) |
|---|---|
| 1 | 90.995 ± 0.005 mm (3.58248 ± 0.0002 in.) |
| 2 | 91.005 ± 0.005 mm (3.58287 ± 0.0002 in.) |
The piston is marked with the piston size (1) on the piston crown. The pistons are available in two different sizes in order to achieve the desired oil clearance. Select the piston size that corresponds to the engine block cylinder bore diameter grade markings for each cylinder.
The chart below identifies the two piston sizes.
| Piston Marking | Size mm (in.) | |
|---|---|---|
| Metal to Metal | Metal to Coating | |
| 1 | 90.995 ± 0.005 mm (3.7793 ± 0.0002 in.) | 90.970 - 91.000 mm (3.7783 - 3.7795 in.) |
| 2 | 90.965 ± 0.005 mm (3.7781 ± 0.0002 in.) | 90.980 - 91.010 mm (3.7787 - 3.7835 in.) |
Typical coated piston shown in illustration.
The coated pistons are serviced with the piston pin and connecting rod pre-assembled. The coating material (6) is applied to the piston after the final piston machining process. Piston installation into the cylinder bore requires slightly more pressure than that required for non-coated pistons. The bonded coating on the piston will give the appearance of a line-to-line fit with the cylinder bore.