Perfection is Almost Good Enough

After five years of development, with the V-10 ready to go into production, disaster struck, when his molds were destroyed in a foundry fire. More than $350,000 in molds and five years of time vanished. However, Conley retained the mold masters from the V-10, and realized he had plenty of knowledge to build on.

With steely determination over a period of additional years, he carefully redesigned his tooling to produce V-8 components, and thus was born the Stinger 609.

According to Conley, the first units of the Stinger engine burned oil so badly they filled a room with smoke in seconds. He discovered the problem was too much oil being pushed up into the cylinders, and though he did not realize it at the time, his honed cylinder surface was too smooth.

“The problem was that the molecular size of oil does not scale down,” he explained. “I thought this was caused by the rings, and spent months assembling engines, making new liners, honing and decking the liners, re-designing the rings and pistons, and testing to no avail.”

Digging deeper into the science of ring and cylinder design, he learned about the nuances of crosshatch, including the proper angle and depth required to create valleys to retain the oil.

“At the time, I did not associate Sunnen with a solution to the problem,” Conley said. He continued, “I was honing with the MB 1660, but came to learn my surface finish was too smooth. So, I got a very coarse, 80-grit, 5-hardness J25 silicone carbide honing stone. This produced nice surface valleys for the oil to be retained, but I had not accounted for the surface peaks.

He added, “After installing rings with an end gap of 0.003-0.004 in and running the engine, the end gap suddenly increased to 0.012 in, because the rings were abrading the peaks off the cylinder finish, and the oil issue returned. Bear in mind, we are using stepped cast iron rings only 0.062 in thick, without an oil control ring because there’s no space for one.”

After consulting with Sunnen engine experts, Conley determined that plateau honing was the answer. Plateau honing, a second pass with a brush or milder abrasive, removes the surface peaks left by the initial pass. It creates a surface profile that resembles a series of plateaus, providing a much greater bearing area, while maintaining the crosshatch valleys for oil retention.

“I once ran a set of new rings in a cylinder that had been plateaued and one that was not,” Conley added. “The plateaued cylinder had no ring wear after run-in. The end gap did change slightly, but this is probably cylinder wear rather than ring wear, because so much happens so fast in these small engines.”

Today, honing continues to be an important step in creation of Conley’s quarter-scale beasts, and he attributes much of his honing knowledge to the company.