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Diamonds are a Block’s Best Friend for Honing

Engine remanufacturer Jasper Engines & Transmissions and engine builder White Performance & Machine are two shops with different needs that illustrate how new diamond honing abrasives technology from Sunnen simplifies the boring process, cuts cycle times as much as half, and improves dyno results.

Posted: January 27, 2012


The sophistication and precision of OEM automotive engines today often exceed that of race engines from a few years ago, leaving no margin for error in honing. Combustion efficiency is up, oil consumption is down, partly as a result of improved bore geometry and ring seal. Clearances and surface finish specs have tightened dramatically as new ring and piston technologies proliferate. Materials and surface coatings have evolved, and some now require diamond honing.

Keeping pace with these changes and staying ahead of them, Jasper Engines & Transmissions and White Performance & Machine are two businesses with vastly different types of work that illustrate how new honing technology, and particularly diamond honing abrasives, can improve cycle time, product quality, and cost, not to mention horsepower and torque.

The Jasper Engines and Transmissions plant (Willow Springs, MO), opened in 2004 and has ridden the market upswing for remanufactured engines brought on by the economy, the common-sense environmental rationale for recycling sound components, and high demand from the marine market.

Originally dedicated to small block 350s, the plant processes about 15,000 engines per year and plans to move into big block and performance work. “We are building stock engines now, but are already doing crank balancing for big blocks and expect to move into light performance engines,” said plant manager Matt Gregory.

As originally configured, the plant used two pairings of a boring mill and a Sunnen CK-21 hone, with each mill/hone pair run by one operator. The CK-21 requires the honing tool to be manually started in each cylinder bore, so the demand on the operator’s time is high – a drawback in a production environment.

“There was no good alternative for the CK-21 at our production levels at the time and we had been reluctant to move into a vertical honing machine because of fixturing costs, but Sunnen showed us the new SV-410 automated vertical hone before its introduction at IMTS 2010,” recalls Gregory. “This is a much heavier duty CNC machine with a 10 hp servo-controlled spindle and powerful tool-feed system to drive diamond or CBN tooling. The automation features of this machine would allow us to immediately increase our capacity, while the power of the machine makes it capable for harder metals and heavier blocks if our part mix changes.”

After the operator hits cycle-start on the SV-410, the entire process is automated. The machine uses a guide pot to start the hone head in each bore. It then indexes the honing tool between each bore, tilts the block for access to each bank of cylinders, and automatically rolls the block over at the end of the process to dump the oil. Crosshatch angle is set via the control screen and easily changed for any ring application.

The servo fixture adapts to any angle V-block via the setup screen, and can rotate a 500 lb block in one second, bank to bank. Full-height/walk-in access doors allow easy part loading. Setup is simplified with a multi-axis hand wheel for fine-tuning vertical stroke, tool feed, column position and optional cradle position. The machine is also designed to use in-process or post-process air gaging for integrated SPC data collection, as well as automatic compensation of size, taper and straightness.

“Our incoming bore size is generated by a boring bar that is targeted to leave 0.0035 in to 0.0055 in of stock in the bore,” explains Gregory. “The honing operator simply tells the control what block is in the fixture and what the oversize should be, then hits cycle start. The honing machine senses the size and knows what to do to produce the finished bore. It’s a real advantage to have the programs setup for a 350 or 262 and actually have the oversizes for the bores programmed in.”

The honing line has since been reconfigured so that one operator now runs two hones (a CK-21 and the newer SV-410) and one operator runs both mills and installs the torque plates. “The big advantage is the simple setup and the fully automated cycle, which allow us to produce high quality cylinders for the lowest cost per bore,” notes Gregory. “Stone wear is automatically compensated and it’s precise, which is a great advantage in our application. The ‘knowledge’ in the control is head and shoulders over the CK-21.

“We have also been impressed with how easy it is to keep this machine clean,” he continues. “The coolant is magnetically filtered and has a paper separator, too. This eases maintenance and keeps the machine in production for more hours. One adjustment we had to make was to check for obstruction from the torque-plate gasket hanging out in the bore, which an operator would catch on a manual machine. An obstructed bore can wreck a set of honing stones.”

As a builder of stock engines, Jasper aims for +0.0005 in to -0.0003 in on bore size, with a range of 15 Ra to 25 Ra on finish and less than 0.0005 in out of round. Using a single stage honing tool on the SV-410, the honing cycle is programmed for 90 percent roughing and 10 percent finishing with a slow feed rate on the abrasives. Plateauing is done offline. Several brands of piston rings may be used, all of them low tension.

“The automation of this machine makes much better use of our labor, freeing the operator to run the manual hone, while another operator can run two mills and do torque plate installation,” adds Gregory. “We also have the honing capacity and technology to handle growing volume and variety in our blocks, as our business evolves.”

Jasper Engines and Transmissions, PO Box 650, 815 Wernsing Road, Jasper, IN 47546, 812-482-1041, Fax: 812-634-1820,

Fred White is the owner of White Performance & Machine (Kingsport, TN) and a former drag racer with a full-service 16,000 sq ft shop and eight employees located in Kingsport. “Our bread and butter is custom high-performance engines for street rods and circle track. We’ve built a strong business in high-performance marine engines, too,” states White. “We also build stock engines and ship crate motors all over the world, as well as provide machine services to other shops.”

The dyno-equipped shop is self-sufficient, with five CNC machines, including EDM, along with crankshaft grinders, balancers, assorted manual machines and all types of gaging and measurement equipment. White Performance does it all, from contract machine work to engine installation.

“We hone about 200 blocks per month for ourselves and others, including high nickel, CGI, Nickasil, aluminum, regular cast iron, GM Bow Tie, Dart, Honda, Toyota, along with big-bore Chevy and Ford blocks – whatever comes through the door, even air compressors with 7 in bores,” explains Chris Webb, a machinist with 40 years of experience who came to this shop two years ago from Morgan-McClure Racing (Abingdon, VA), where he worked for the Sprint Cup Kodak No. 4 team.

The plant was using an older Sunnen CV616 honing machine with vitrified abrasives when Webb came on board with NASCAR shop experience. “Even the most experienced operator can struggle to get decent results with the 616 and vitrified abrasives. It will still never match the roundness, straightness and finish quality that newer machines and diamond abrasives can produce,” explains Webb. “It takes an experienced operator and a lot of work to get acceptable results with the older technology. Changeovers from one finish to another required belt changes on the machine and took time to set and adjust. All of this adds up to long cycle times on the hone, and reduced performance on the dyno.”

Having used a Sunnen CK21 and diamond tooling in his prior job, Webb was instrumental in convincing White to purchase in late 2009 the newest Sunnen SV-10 with diamond tooling.

“The SV-10 essentially doubled our capacity by cutting cycle time in half, while our quality and dyno results improved immediately,” notes White. The PLC-controlled SV-10 has a separate 3 hp (2.25 kW) spindle motor, as well as a stroker motor, so it has plenty of torque to drive the diamond hone head. The PLC and variable speed motors allow infinitely variable crosshatch angles for any bore diameter and cylinder length – all of which can be changed on the fly.

A patented full-bore profile display shows a real-time cross section of the bore, which takes the guesswork out of removing taper. For unattended operation, the auto dwell feature will automatically dwell the honing action in the tightest areas of the bore. “You can see exactly what’s going on during the honing cycle,” Webb says. The DH diamond hone head provides multi-point abrasive contact on the bore and a cone-style feed system produces uniform feed pressure on the circumference of the tool for exceptional roundness.

“Even putting a torque plate on nearly every part we hone, I can do all this and still complete a block in half to two-thirds the time it took on our 616 without torque plating the part,” adds Webb. “With all the different types of blocks and cylinders we run, it’s a great advantage to have your current setup at your fingertips in the control to quickly make changes.

“Once you set your stroke, speed, load and crosshatch, every cylinder is the same, with no taper or roundness variations, and I can do other jobs in the shop while the machine runs,” he continues. “With the new hone and diamond tooling, our horsepower and torque are up one to two percent on various engine packages we build, and our run-in time on the dyno has lessened.”

The shop runs roughing and finishing cycles with the diamond tool, then plateau hones with a Sunnen brush tool. “Our targets are 0.0002 in or better on size, less than 0.0001 in on out-of-round, with finishes in the range of 35-40 Rvk, 8-12 Rpk and 23-28 Rk, depending on the rings used,” explains Webb. “We take our measurements with a Mitutoyo surface finish analyzer and Sunnen bore gages.”

“This machine will make an inexperienced operator look really good, while an experienced operator will put out much more work with lower cycle times,” smiles White. “The variable speed motors and PLC control permit infinite crosshatch angles for any cylinder length or diameter – on the fly, without belt changes. We take out 0.007 in to 0.009 in, working on a lot of bow tie and Dart blocks which are harder, yet our original abrasives lasted 18 months.

“My one regret is that we did not move up to this machine much sooner,” he adds. “I’d recommend it as a first machine for any automotive shop.”

White Performance & Machine, 3353 East Stone Drive, Kingsport, TN 37660, 423-288-3881, Fax: (423) 288-5892,,

Sunnen Products Company, 7910 Manchester Road, St. Louis, MO 63143, 800-325-3670, Fax: 314-781-2268,,

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