Cylinder Honing
The process of scrubbing the cylinder walls of an engine block with an abrasive tool to create a crosshatch pattern for oil retention and ring seating.
Cylinder honing is a machining process performed on the cylinder bores of an engine block during a rebuild. It uses a rotating tool fitted with abrasive stones (a hone) that is moved up and down inside the cylinder. This creates a fine crosshatch pattern of microscopic scratches on the metal cylinder walls.
This crosshatch pattern is critical for engine longevity. The tiny grooves retain a microscopic film of engine oil, lubricating the piston rings as they slide up and down. Without this oil film, the rings would run dry, causing rapid wear and scuffing of the cylinder walls. Honing also ensures the cylinder is perfectly round and straight, allowing new piston rings to seat (seal) correctly.
If a cylinder is not honed during a rebuild, or if the hone pattern is too smooth or too rough, the new piston rings will not seal, leading to low compression, oil consumption, and blue exhaust smoke. Mechanics check the cylinder roundness with a dial bore gauge before and after honing to ensure it meets factory specifications.