11 Here’s the cylinder wall after a quick first pass. Notice the shadowing in a line straight down the bore directly in front of the head bolt hole. This is warping that developed over time. It was revealed when the honing stones removed the metal on either side of this shallow hole or depression. Even small variances like this can cause sealing problems. When this happens, exhaust gasses are allowed to pass by the rings—instead of pressing down on the piston to produce power.