Engine Rebuild: Honing Cylinder Walls with the Flex-Hone®

When the engine in Bruce W. Maki’s 1999 GMC Jimmy developed a connecting-rod knock, the founder of HandyManleyNess.com found himself at a crossroads. With a book value of $3000, the sport utility vehicle (SUV) was too valuable to scrap, but not worth the expense of a remanufactured engine. Since buying a used engine seemed “risky”, the former auto mechanic decided to remove and rebuild the 4.3 GM V6 piston engine himself.

Engine Parts and Engine Tools
The remanufactured crankshaft kit that Bruce Maki bought from a local auto parts store included all the necessary journal bearings, but required removing the cylinder heads and pistons. So Maki purchased a piston ring set and lower and upper gasket sets, too. Engine tools and equipment included piston ring pliers, a piston ring compressor, an engine hoist, an engine stand, and the Flex-Hone® tool from Brush Research Manufacturing (BRM).

The Flex-Hone® for Engine Cylinders
“If new piston rings are installed,” Maki explains, “the cylinder walls MUST be given an appropriate scratch pattern” to promote piston-ring seating and optimum lubrication. The “scratch pattern” that he describes is achieved by deglazing and plateau finishing. By using the Flex-Hone®, engine builders can remove the polished surface, or glaze, from the walls of engine cylinders. They can also remove the peaks produced by prior honing and machining operations to create a flat, smooth cross-hatch surface. 

Deglazing and Plateau Finishing
“The best way to get the proper scratch pattern,” Bruce Maki continues, “is with an electric drill and a ball hone”. First, he chucked a 4-1/8” Flex-Hone® into a 1/2” drill motor with a maximum speed of 850 RPM. “Many smaller (3/8”) drills spin at 1200 RPM or more, which is too fast for this procedure,” the engine mechanic explained. Next, he applied some 10W-30 motor oil to the Flex-Hone® while spinning. (With its special blend of honing and lapping oils, BRM recommends Flex-Hone® oil instead.)

Cylinder Honing and Engine Block Cleaning
Maki then “ran the brush up and down” each cylinder wall for one minute while running the drill at 850 RPM. “I can tell the angle of the scratch pattern by the angle of the swirls in the oil on the cylinder wall,” he later noted. With his engine honing complete, the founder of  HandyManlyNess.com finished the job by washing the engine block with laundry detergent and hot water. Removing any abrasive-grit debris from cylinder walls is “very important”, Maki added, to prevent “scoring” or other engine problems.