BRM Official Blog

How Flexible Honing Prepares Engine Blocks for Cylinder Sleeves

Posted by Heather Jones on Aug 28, 2015 10:23:43 AM

flexible_hone_automotive_rebuildingFlex-Hone® tools for engine cylinders don’t just impart an oil-retaining surface finish. They remove cut, torn, and folded metal that can interference with proper piston ring seating and sealing. What some automotive mechanics may not realize, however, is that ball hones can also help to prepare engine cylinders for new cylinder sleeves. By smoothing the sharp metal edges on cylinder walls, flexible honing removes burrs that could break off and interfere with proper cylinder-liner installation. 

Professional engine rebuilders and automotive machine shops understand the importance of flexible honing, and use ball hones made by Brush Research Manufacturing (BRM) before installing cylinder liners in engine blocks. In an on-line article from Hot Rod Network, author Steve Magnante describes how one Ludlow, Massachusetts shop used Flex-Hone® tools to deburr and finish the cylinder walls in a high-performance engine block for the Ford Mustang. 

Mustang Engine Blocks

As Steve Magnante explains, the aluminum engine block that debuted with the 2011 Shelby GT Mustang was “unique in mod motor history.” Ford had used aluminum power plants with Mustangs before, but the big block for this Shelby Cobra featured cylinder walls with a special surface coating. Developed by Flame Spray Industries, plasma transferred wire arc (PTWA) technology treats aluminum cylinders with a super-thin, lightweight coating that matches the performance characteristics of heavier, cast iron cylinder liners.

Ford’s design decision reduced the Mustang’s overall weight, and concerns about the durability of the plasma cylinder coating didn’t stop the automaker from using PTWA in post-2011 engines. Yet some Mustang owners remain skeptical. So when the Connecticut owner of a 2011 Shelby Mustang decided that he wanted to install steel cylinder sleeves, he brought his car to the automotive machine shop in Massachusetts. There, engine specialists also determined that the cylinder bores were out-of-round.

Ball Hones for Engine Cylinders

Flex-Hone® tools aren’t designed for out-of-round cylinders. BRM ball hones aren’t built for heavy-duty material removal either. For worn, damaged, or tapered cylinders, cylinder sleeves or liners are a cost-effective alternative to replacing the entire engine block. We’re not sure how the Massachusetts machine shop removed the plasma coating, but Hot Rod Network's Steve Magnante writes that the engine builder “lightly honed the cylinders to show how delicate the factory PTWA coating is”.

What readers know for sure is that the Massachusetts machine shop used Flex-Hone® technology to remove “bits of loose material and sharp edges (that) can break and prevent free passage of the sleeve inserts during installation.” Given the parent material of the engine block, we can also guess that a BRM ball hone with aluminum oxide (AO) abrasive was used. AO Flex-Hone® tools are perfect for softer metals, and come in a variety of tool diameter and grit sizes.

Get the Automotive Engine Builder Case Study

BRM ball hones have long been a favorite of engine rebuilders. For another great automotive case study, learn how a New Jersey remanufacturer of car and truck engines used Flex-Hone® technology to improve the surface quality of cylinder liners in rebuilt engines.

Download the Engine Rebuilder Application Guide   

Topics: Engine Rebuilds