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Holley’s 1966 Mustang Is a HOT-Bed for Engine Innovation
Holley's Ti-VCT test mule
The Corner Horse moniker comes from the Kentucky Quarter Horse, something of an everyman's hot rod in its own right. Bred to work during the weekdays and race during the weekends, the breed was favored by ranchers for its prize-winning speed and good manners, which echoed Tom's goals for the build.
Starting out as a six-banger California car, Tom had Holley's Scott McLaughlin inspect the once-repainted Mustang before clicking "Buy It Now." Other than a "period-correct," slide-hammer dent repair in the rear quarter, it checked out as a solid foundation for Holley's Ti-VCT development car. "I'm always a little nervous about repainted cars—it's so easy to hide damage," Tom said. "But for a fastback Mustang, it was reasonably priced." After bringing the car back to Holley's HQ in Bowling Green, Kentucky, Tom worked with Michael Miernik on Corner Horse's concept rendering to pen the vintage road-race look.
The first stop after teardown was DSE, where Tom's son, Blake, would take the reins as lead fabricator. After mediablasting, Blake repaired the rusty cowl and footwells before turning his attention to the damaged quarter. Once the preliminary bodywork was completed, DSE's Mark McDonald began work on the chassis. The factory sheetmetal "framerails" were removed, and Mark welded in box rails that ran from the rear bumper to the front subframe, tying the chassis together while also providing the new pickup points for DSE's Quadralink rear suspension.
From there, Mark also built the rollcage to further stiffen the chassis while also bringing track safety up to snuff. Up front, DSE installed its Aluma-Frame front crossmember, which utilizes tubular control arms and Corvette C6-style spindles and brakes with heavy-duty SKF hubs. A Ford 9-inch was stuffed with gun-drilled Stielow Engineering axles with C6 Corvette ABS reluctors, along with C6 rear brakes and 3.89 gears on an Eaton Truetrac.
To fit the sticky 275-front, 335-rear BFGoodrich Rival S tires, Blake fabricated steel fender flares on all four corners with DSE's mini-tubs and shock-tower eliminators, which also gave Corner Horse the vintage road-race feel Tom was after. "I saved up photos of vintage Ford race cars, Mustangs and Cobras," he said. "The inspiration for the flares, wheels, and spoiler was a Trans-Am vibe, but in a streetable car." The tailpanel was modified to house a motorcycle filler cap before Blake focused his attention on the sheetmetal rear seat delete, which hides the ECU and battery in a custom floor compartment.
Once the main fabrication was completed, Corner Horse was sent to Sled Alley in Clinton, Michigan, for final prep ahead of paint. Matt Gurjack worked to finalize the panel gaps while also re-leading the original seams before shipping the car to Dutchboys Hotrods in Kalamazoo, Michigan. The body was block-sanded and prepped, and PPG True Blue was laid down with Porsche/Audi creamy white stripes, with just about any surface left over shot in semi-gloss black.
Sled Ally was tasked with the final assembly, bringing the pieces together in the weeks ahead of SEMA—heck, Tom didn't even get to hear that Aluminator breathe until the show began! You can expect to see Holley's twin-cam test mule out and about in 2017 as it begins stretching its legs with Ti-VCT control.
Holley's Ti-VCT Controller
The majority of camshafts have fixed variables, meaning they're optimized for a very specific rpm range. Typically, cam position is set once during engine assembly. However, with modern engine controls and timing components, the cam (or cams, in the case of the Coyote) can be advanced or retarded while the engine is running to broaden the torque and power curves. They can even create artificial overlap to feign the idle of a choppy cam, such as the "ghost cam" idle found in the S197 Boss Mustang (with the Track Key).
This is done with a cam phaser, a two-piece cam gear that uses oil pressure to hydraulically adjust angle between the chaindriven and camshaft halves of the timing gear relative to the crankshaft. Ford's iteration, Twin Independent Variable Cam Timing (Ti-VCT), can phase through 25 degrees of cam rotation (12.5 degrees advanced or retarded) and is notable among current domestic V8s for being able to independently adjust the intake and exhaust valve timing, thanks to its dual overhead cam (DOHC) configuration (with a phaser for each intake and exhaust cam), whereas LS, LT, and Gen III Hemi engines can only adjust the single cam that carries both the intake and exhaust lobes—though the Viper's 8.4L V10 uses a concentric "cam-in-cam" to independently adjust intake and exhaust lobes.
Most high-performance Coyotes lock out the Ti-VCT phasers to prevent cataclysmic piston-to-valve contact when using an aggressive camshaft. While some kits limit the phaser's travel—providing at least some timing control—you'll often see kits that lock or remove the phasers entirely. While this typically optimizes the cam timing for high-rpm applications, you lose substantial midrange numbers. In a box-stock Coyote, there's more than 50 lb-ft of advantage at 3,000 rpm compared to locked cams, with substantial gains all the way to peak horsepower. Holley's Ti-VCT controller is an add-on module for its popular Dominator and HP EFI systems that picks up the performance data it needs from the shared CAN-BUS connection. Holley provides adjustable cam tables in its tuning software. "We have a variety of base maps. You find one closest to your application and load it in," explained Adam Laymen, Holley EFI systems manager. "Obviously, if you're going outside the boundaries for what we've mapped, you are on your own a bit. But even if you've never mapped variable valve timing before, we've set it up in very simple terms so anyone who can understand lobe-separation angle and lobe centerlines—and what you're trying to accomplish with them—can build a table."
Holley developed its variable valve timing controller on the four-cam Coyote, as it proved to be the most complex platform, but the company expects to release LS and LT versions in the near future now that the bulk of development is saddled on Corner Horse.