Cylinder Block Distortion

WARNING: This page is about a different car, the 2006 Nissan Xterra. However, it is still accessible from the selected car via links, so may be relevant.

Using scraper, remove gasket on the cylinder block surface, and also remove engine oil, scale, carbon, or other contamination.
CAUTION: Be careful not to allow gasket flakes to enter engine oil or engine coolant passages.
Measure the distortion on the cylinder block upper face at some different points in six directions with straightedge and feeler gauge.
Limit : 0.1 mm (0.004 in)
If it exceeds the limit, replace cylinder block.

Fig 1: Checking Distortion Of Cylinder Block Upper Face

Courtesy of NISSAN MOTOR CO., U.S.A.