Cylinder
honing tools are used to deglaze the walls of cylinders in gasoline and diesel
engines. Over time, a piston's reciprocating movement will polish the cylinder
walls to a smooth finish, preventing the piston ring from mating with the
cylinder bore and providing an adequate seal. Glazed cylinder walls also cause friction and lubrication problems since
engine oil won't adhere properly to a mirror-smooth surface. The way to break this glaze is with an engine hone that also promotes optimum
lubrication.
Choosing Cylinder Hones for Engine Repairs
Engine Repair Shop.com is an automotive website run by Bill
Koustenis, a machine shop owner and self-described "car nut" who recommends
cylinder honing tools for "reringing the engine". A member of the Engine
Rebuilders Association (AERA), Koustenis compared traditional stone hones to
the Flex-Hone tool from Brush Research Manufacturing (BRM). Although honing
stones are "probably the oldest and most
common type of portable hone," Koustenis favors flexible honing for preparing
engine cylinders.
Engine Blocks: Problems with Stone Hones
The "problem" with portable honing
stones, Koustenis explains, "is that it is impossible to really end up with a
straight and round cylinder". Engine cylinders with excessive wear should be
"bored to the next oversize" instead. Engine builders who use honing stones can
ruin the engine block, a problem Koustenis has seen "plenty" of times. "I
really do not feel," the former drag racer explains, that stone hones "have any
place in quality engine repairs."
Engine Rebuilds: The Flexible Honing Solution
Self-centering and self-aligning to
the bore, a Flex-Hone is a flexible,
resilient cylinder honing tool with a soft cutting action. Built with a stiff
metal stem, flexible nylon strands, and abrasive globules that come in a
selection of grits and abrasive types, the tool "removes hardly any
material and works great with almost any type of piston ring," Bill Koustenis
explains. He adds, "We use this type of hone when a performance or racing
engine is being 'freshened up' during the racing season."
The Flex-Hone also promotes optimum lubrication. Unlike rigid
hones, which produce uneven or unidirectional grooves, the tool produces
a plateau surface finish for improved oil retention. For more information about
the importance of a plateaued cylinder wall finish, click here for this technical book from BRM. It's one of many
in-depth publications available from the Brush Research website.
Author's Note: This CR4 blog entry originally appeared in BRM's Flex-Hone Blog.
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