Ridge Reaming an Engine Block
A ridge reamer is used to remove the ridge from the top of the cylinder’s bore. The ridge is caused by the cylinder wall wearing from ring travel just above the top of the compression ring. This wear leaves the area above ring travel unworn. It's best to remove this ridge before removing the piston. This will prevent any damage to the piston ring groove lands during piston removal.
Hone the cylinder to a smooth finish for the new piston rings. Do things in small increments so too much material is not removed. A flexible or a beaded hone is used to remove glaze and restore the cylinder's finish. If left, the ridge can damage new piston rings after the engine is started. This will result in blue gray smoke after the rebuild. This is from engine oil bypassing the faulty rings and entering the combustion chamber.