The Flex-Hone® for Honda Civic Engines

The Honda Civic is one of the best-selling cars of all time. Introduced in 1972, the Japanese automobile is known for its reliability and affordability. Like other vehicles, however, high-mileage Civics experience engine problems ranging from poor fuel economy to cracked blocks. For The_Acid_Beaver, a member of SOHC Honda Forums, an engine swap became necessary when his parents’ 1991 Civic hatchback “died”. The automotive hobbyist surely made Mom and Dad proud when he tore down, rebuilt, and re-installed the Honda D15 engine using tools such as the Flex-Hone® from Brush Research Manufacturing (BRM).

Honing Tools for Cylinder Reconditioning
The Flex-Hone® is a versatile, flexible cylinder honing tool used for deglazing and refinishing cylinder walls in all types of gasoline and diesel engines. Unlike rigid honing stones, BRM’s flexible engine hone does not have a high side and a low side that can remove too much material. Because it’s self-aligning and self-centering to the bore, the Flex-Hone® keeps a constant pressure against new or worn cylinder walls. The Flex-Hone® is also self-compensating for wear, meaning that the tool’s abrasive globules provide a consistent low-temperature, soft cutting action for plateau finishing and optimum lubrication.   

Flexible Hones for Cylinder Walls
Before starting his engine rebuild project, The_Acid_Beaver “consulted many knowledgeable people” about tools and techniques, he explained. Although the hobbyist had “some grave concerns” about the rust in one of the Civic’s cylinders, he listened to the automotive experts at SOHC Honda Forums. “Each and every one said that a good honing will take care of the rust,” The_Acid_Beaver recalled, so he tore the engine down.  Thorough in his work, the do-it-yourselfer even had the engine block hot-tanked before replacing the valve stem seals and reinstalling the springs, retainers, and keepers.

How to Hone Cylinder Bores
“The next big thing I had to do,” The_Acid_Beaver recalls, “was to re-hone the cylinder bores.” First, he clamped the mandrel of a 3-inch Flex-Hone® into the chuck of his father’s handheld, variable-speed Milwaukee drill. BRM’s flexible engine hone was “the perfect size for Honda D-series engines”, he explained. Next, the engine rebuilder generously lubricated the Flex-Hone® and inserted it into each cylinder while the tool was spinning. “Slow and steady is the pace you need,” he added, noting that “as long as you don’t crank your trigger all the way”, lubricant won’t “get everywhere”. 

Warm or Hot Soapy Water – Not Brake Cleaner
Although The_Acid_Beaver used automatic transmission fluid (ATF) as a lubricant instead of the Flex-Hone® oil that we recommend, he removed the rust and imparted a cross-hatch pattern to the engine’s cylinder walls. Finally, he washed the block with hot soapy water to remove leftover dust and debris. “Why not just spray it down with brake cleaner?” he asked SOHC Honda Forums. “That won’t get all the metal particles off the cylinders,” he answered. Using warm or hot soapy water for cleanup after flexible honing is good advice, and shared by experienced Flex-Hone® users such as Caterpillar.