"This is just our mule engine," says Stock Eliminator racer John Calvert. That may be, but this mule looked much more like a thoroughbred when we watched John and noted engine builder and tuner Kenny Duttweiler spin Calvert's supercharged, four-valve motor up on Duttweiler's dyno. Calvert decided to tune the engine on the dyno after a few runs in his updated 2014 Mustang that runs in NHRA's AAA/Stock Eliminator class.
In previous testing, the Mustang has already run 8.80s on a 9.70 index, which is already impressive—remember, this is Stock Eliminator we're talking about. But it's the engine we really came to see. Calvert says that he and engine builder Eric Jones collaborated on assembling the engine that consists of a 0.070-over Coyote 5.0L short-block with a stock crank, Manley rods, and Mahle pistons. For cylinder heads, Calvert is running the Ford Racing CNC-ported four-valve heads along with four "longer duration" hydraulic roller cams from Comp Cams. As you can imagine, he was less than specific about the cams. But the real hero deal is the Ford Racing 2.9L Whipple supercharger and Accufab mono-blade throttle-body.
The main reason Calvert was on Duttweiler's dyno was to get an accurate tune on the engine using one of Holley's brand-new wiring harness packages for the Coyote engine. As of now, there are only about two or three of these in existence to mate Holley's Dominator ECU with the four-cam Ford engine. Holley's Robin Lawrence was also on hand to lend some tuning expertise. The big news was how much power this package put out. We were there long enough to witness multiple pulls from 4,000–9,000 rpm, where the Ford made fantastic power. We saw 1,000 hp flash up on the screen a couple of time during the day, but the run we recorded produced slightly less at 996 hp at 8,400 rpm.
Perhaps even more impressive was the 742 lb-ft of torque peak that occurred a 5,400 rpm, producing an incredibly wide 3,000-rpm powerband. Most normally aspirated engines generally produce a powerband that spans 1,500–1,800 rpm. A well-designed supercharger package might expand that a bit, but clearly the combination of four valves per cylinder and that Whipple blower make for a lethal combination of both peak horsepower and an incredibly wide powerband. Good racers know that while peak horsepower is important to a quick e.t., excellent torque in the midrange also contributes to improving acceleration.
One key to serpentine beltdriven superchargers is to employ more than a 180-degree wrap around the blower pulley. This improves traction and prevents belt slippage that can cost horsepower. The Thump RRR Racing billet belt tensioner probably helped too.
It may only be 311 ci, but when you can squeeze 996 hp out of that, the world will take notice. That computes out to 3.20 hp per cubic inch.
While it's obvious that the Whipple 2.9L blower tends to take center stage cranking out roughly 14 psi of boost, let's not forget the CNC-ported four-valve Ford Racing heads and the contributions from the Comp roller cams. Calvert also says he was using stock Ford coils.
Calvert experimented with two different headers; these are from American Racing and have 17⁄8-inch primaries, of equal length tubing, and a merge collector. He also tried a set of 2-inch primary pipes with a much larger 4-inch collector, but the differences (at least at first glance) in power were negligible.
