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iron-sleeved cylinder bores, including blocks machined from forged and heat-treated aluminum billets.
Dart combines two advanced technologies—diamond hon- ing abrasives driven with a programmable spindle, followed by profilometers to measure the peaks and valleys of cylin- der surface finishes—to replicate “best” block finishes and ring seal. “Experienced racers have always had their favorite blocks, ones that ran better than others,” said Maskin. “We’ve learned through experience that it wasn’t the block that made the difference, but how your honing process worked for that exact block, since similar blocks might pro- duce much less horsepower. Once you understand the finish you need from honing—and we know these numbers now thanks to profilometers—you can make the bad blocks good, too. We use honing to achieve the ideal Rvk [valley depth average], Rpk [peak height average], Rk [core roughness depth], and crosshatch to finish a block for a given applica- tion,” Maskin said.
A Chevrolet performance small block is being honed at Dart Machinery in the new SV-20 flexible honing system from Sunnen.
Knowing the desired result, the honing process can be tweaked to achieve the result in any block. “If you go from a 200 brinnel block of cast iron to a much tougher CGI [com- pacted graphite iron] block, you need to know how to achieve your finish numbers in the different materials,” said Maskin. “Finishes also must account for the type of fuel burned in the engine, which could be alcohol or natural gas.”
HAIMER Cool Flash:
Optimal cooling – Even at the speed of light.
Tooling Technology Shrinking Technology Balancing Technology
Haimer USA, LLC | 134 E. Hill Street | Villa Park, IL 60181 | Phone: +1-630-833-1500 E-Mail:
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www.haimer-usa.com
See us at Booth #W-1452 40
ManufacturingEngineeringMedia.com | June 2014 Measuring Instruments
“Honing is all about sealing the rings to the cylinder wall,” said Maskin. “The key is valley depth. Too deep and you have too much oil in it, slowing the engine down with friction. Too little val- ley, and the rings can hydroplane across the valleys and you lose seal. Then, you have to run thicker oil. Unless oil can re- side in the valleys, it sits on the cylinder wall and must be thick not to be torn off by the rings. We think valleys need to be in the mid to high 30 microinches (0.000030"/0.00076 mm) to really seal a race engine strongly, and deeper in the mid to high 40s [microinches] for a more conventional engine. “For some blocks using today’s steel rings, we hone for peaks of 12–15 microinches (0.000012–15"/0.00030– 0.00038 mm) or smoother. When we turn the short block over manually with a wrench, the rings will knock the
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