More airflow for Ford's SVT V-6 - SVT Contour sports sedan

Automotive Industries, Feb, 1998 by Lindsay Brooke

Extrude Hone Corp. had the process to do it. Working together, the automaker and this supplier made custom-ported cylinder heads a reality for niche vehicles.

Being successful as a niche-market player often requires unlikely resources--and partnerships. Just ask Ford's Special Vehicles Team. Its SVT Contour sports sedan launched last March, has garnered rave reviews, due partly to the use of a manufacturing process commonly used in the aircraft industry and developed by a company little-known to automakers.

When given the job in April 1995 of transforming the staid Contour into its firebreathing alter-ego, the SVT knew it had most of the "right stuff" already in hand. In particular, Contours 2.5L Duratec V-6 has a strong bottom end, and its dohc, 4-valve-per-cylinder heads give it excellent rev potential. 7b unlock the extra power obviously lurking inside, all the little V-6 really needed was more airflow, the team reckoned.

Sportier camshafts, a 5mm larger throttle body (60mm bore), larger fuel injectors, a less restrictive air cleaner and a lightened flywheel immediately perked up the V-6. "But we couldn't maximize these changes without a nice uniform, streamlined flow path," asserts engine technologist Dave Dempster, who helped spearhead the 2.5L's development Increasing the linear velocity within the head and manifold "meant making the ports and manifold tracts more efficient," he explains.

That meant polishing the nodular cast walls of the V-6s cylinder head intake ports and intake manifold runners to a smooth, even finish. It's known as custom-porting, but such attention to detail is rarely possible for automakers. Conventional dunking holds that they cannot afford to lavish even 5,000 engines per year (the SVT Contour program) with speed-shop-levels of hand labor. Too slow. Too inconsistent Too costly.

Ford SVT isn't a conventional operation, however, and Dempster's colleagues soon discovered a solution among the ads in one of the Ford hop-up magazines. A company based in Irwin, Pa., called Extrude Hone Corp. custom-ports all types of cylinder heads using a unique process, in which an abrasive medium is extruded under pressure through the ports, polishing them thoroughly (see diagram, p. 148) SVT got in touch.

[Diagram OMITTED]

"When Ford approached us, we were delighted," recalls Larry Rhoades, president of Extrude Hone. "We'd been looking for a niche-vehicle program. We wanted to prove, at the SVT Contols volumes, that our process can give absolutely consistent performance port-to-port, runner-to-runner and engine-to-engine."

That it does. Fords Dempster claims port and manifold runner variability has been 21% or less since production began last spring. That's compared with an industry-nominal 5% variability. "Engine to engine, when randomly tested on the dyno, these V-6s are within 2% of each other in power output--that's excellent," he says. Airflow through the heads is "significantly boosted," Dempster says. According to Rhoades, each honed intake runner shows a 2 cubic feet per minute (cfm) improvement.

Such use of the Extrude Hone process is an outgrowth of the company's first commercial application in the mid-1960s. It was a Westinghouse aerospace contract -- deburring tiny passages within a valve body on the F4 Phantom fighter jet's fire control system. "The spec was ultra-precise -- it had to be burr-free under 20-power magnification," Rhoades recalls.

Aerospace remains one of Extrude Hone's biggest markets. Marketing Director John Matechen claims the process is used by virtually every commercial jet engine maker to polish micro-sized passages after CNC milling. The automotive business grew out of contract work done since the '70s for racers, including Roger Penske. In those days the process was not easy to automate in volume; now the Extrude Hone machines are totally automated, and can process each 16-valve cylinder head in 90 to 120 seconds. Diesel fuel injectors, honed at 3,000 psi, comprise another of the company's major markets.

Prior to the Ford SVT program, the only other automotive OEM cylinder head job was a 600-unit run for another niche performance car, the Williams-Renault Clio.

Extrude Hone also markets its patented honing machinery, having sold over 2,000 of them worldwide.

The proprietary abrasive media is polymer-based, with a unique rheology. According to Rhoades, the material itself has shear-stiffening and shear-softening properties -- under increasing shear stress it becomes a solid. Its ability to "plug flow" allows it to drag along the workpiece wall. The polymer is made by Extrude Hone in-house in literally thousands of viscosities, which enable it to efficiently move through passages as tiny as a 0.004-inch injector nozzle -- and into even tinier hypodermic needles.

The material is blended with a wide variety of abrasives, including diamonds, depending on the surface finish spec. The Ford SVT components are polished to a satiny sheen using a single, medium-grit abrasive.

Cost and supplier-sourcing issues determined that the porting job would not be done by Ford in-house, says SVT supervisor Tom Lavander. The program's supply chain begins at Ford's Nemak casting plant in Mexico (early castings were supplied by the Windsor, Ont., plant). Nemak ships head castings to Extrude Hone's new 100,000 sq. ft. Irwin plant by truck, the batch sizes deterMined by SVT Contour assembly schedules. A typical batch is 300 heads. At Irwin, incoming castings are numbered for tracking, then processed. After honing, each component is cleaned, receives a QC check and airflow is measured against spec.