High-performance piston rings require ‘fool-proof’ cylinder honing
Los Angeles—While vital to performance, the piston ring is the poor stepchild of the high-performance engine, said Keith Jones, technical Expert at Phoenix-based Total Seal. “They get blamed for just about everything. If there is a compression problem, it’s the piston rings. If there is oil consumption, it’s the rings.”
Since 1967, his company has been manufacturing high-performance piston ring sets installed in racing engines used in competition events ranging from IRL (Indy), NASCAR, World of Outlaw sprint car and other racing classes. To stay informed of customer needs and satisfaction, Jones actively solicits feedback from customers, particularly questions concerning performance and critical installation procedures.
Except for its standard automotive line, the countless different ring sets that Total Seal offers are for customized engines, each having many individualized requirements, including cylinder block materials and piston ring designs. Of those, it is particularly important that the piston rings precisely maintain 100-percent contact with the walls of the block’s cylinder bores. Otherwise, performance problems such as compression blow-by and oil leakage can cause severe, if not catastrophic, problems, he said.
Providing the needed consistent contact between piston rings and cylinder bore almost always requires resurfacing of the bores in racing applications, either because the bores are not perfectly round, have been damaged by previous ring or piston failure, or other wear factors. In any such cases, resurfacing the bores can be a challenge.
“High-performance engine blocks have changed a great deal over the past couple of decades,” Jones said. “One of the most noteworthy changes is the hardness of the block metal, which can be several times harder than it used to be. This has dramatically affected cylinder ring installation requirements because it is now crucial for the customer to achieve proper ring fit inside the cylinder bore at the time of installation.”
To facilitate proper cylinder bore surface preparation and piston ring-to-bore fit, Jones and other high performance ring manufacturers and distributors recommend the honing of cylinder bores to exacting tolerances (within a few microns). The procedure ensures that excessive compression blow-by and inadequate cylinder bore oil retention are avoided at the outset.
Simplified honing solution
Since bores differ widely according to block hardness, design and engine wear conditions, the proper honing of bore surfaces can become challenging. Jones recommends the Flex-Hone, produced by Brush Research Manufacturing, in Los Angeles.
The Flex-Hone is a ball-style tool characterized by a shaft with small, abrasive globules that are permanently mounted to flexible filaments. The tool is available in many sizes with a wide selection of grit material, he said, adding that it works well when handheld because the design is automatically self-centering.
The cross-hatching capabilities of the tool are integral to the cylinder bore surfacing requirements of most internal combustion engines, ensuring that proper oil retention will be maintained in the cylinder bore walls at all times, he said.