For some, money is no object. If someone with the wherewithal happens to be as horsepower crazed as we are, things can get pretty wild when the idea of a budget is cast aside.
That’s all you really need to know about why the Hurst/Kenne Bell pairing is now tackling a 1,100-crankshaft-horsepower example for a truly limited Hurst/Kenne Bell Mustang. A customer wants one, so Kenne Bell is stepping up with a bigger, 4.2-liter blower instead of the mere 3.6-liter behemoth fitted to the garden-variety 750-horsepower models.
The larger blower has engendered detail improvements in the existing Kenne Bell Mustang GT fitment, namely a second drive belt, modified fuel rails and a whole new attitude in the torque and horsepower categories.
Furthermore, with the engine longevity threatened by quadruple-digit power figures and the owner eager to have the best of everything, this engine uses some Voodoo magic mixed with a Coyote howl to make its mark. That’s right, not only is this Hurst/Kenne Bell build starting with a 2017 Mustang GT with just 7 tender miles on the odometer, but it’s also an engine swap. The Coyote is out, replaced by a Voodoo motor so thoroughly modified there’s precious left of it; save the block and those gorgeous cylinder heads.
Hurst-Kenne Bell R-Code Mustang
Built as a collaboration between Performance West Group, Hurst and Kenne Bell, the 2017 Hurst-Kenne Bell R-code Mustang is a celebration of the Hurst legacy with a modern Mustang performance machine. It is also a showcase for what the Kennne Bell superchargers can do for these cars.
“I couldn’t think of anybody I would rather work on a high-end Mustang with than Kenne Bell. He (Jim Bell) is one of the few that goes to the effort to do a 50-state, street-legal supercharger with an EO that’s good in any state or Canada,” Larry Weiner of Performance West Group told us.
You can learn more about this limited run of 50 vehicles here, but a truly special example of this lineage will receive the big-power Voodoo engine you see coming together in this story.
The people making it happen are top notch as well. The core engine was developed and assembled by Gil Nevarez, of Nevarez Racing Products/Shelby American Automobiles where he was the power behind the Shelby 1000 S/C and its derivatives. Ken Christley has been Kenne Bell’s chief technologist and all-around hands-on developer for years now, and this installation is a natural progression of the standard Kenne Bell blower kit he designed for late-model Mustang GTs. And, much of the installation has been in the able hands of Ricardo Topete at GTR High Performance.
Eventually the car will gain its Hurst treatment at Larry Weiner’s Performance West Group where he builds all the modern Hurst cars and, of course, Jim Bell of Kenne Bell is on hand with his specialty fuel system skills (and to take everybody to lunch).
The Long & Short Of It
As just noted, this engine began as a 5.2-liter Voodoo production engine obtained separately from the 2017 Mustang GT starting point. That said, the 5.2-liter block, oil pump, oil pan and cylinder heads are the only major Voodoo to make it into the final long-block. So, if you are looking to replicate this build, you could arrive at 1,100 horsepower by starting with pieces from Ford Performance and the 5.0 from a Mustang GT.
There’s also a significant aftermarket presence on this engine. From the intake manifold upwards the engine is all Kenne Bell. Likewise, the front engine dress is all Kenne Bell except the water pump, which came from the Mustang GT 5.0-liter engine, as did the alternator.
We’ll also note Jim Bell is not a fan of Ford’s 180-degree crankshaft, saying it vibrates too much. He also understands a supercharged engine doesn’t need to rev to 8,200 rpm like the stock Voodoo to make power. In fact it’s not even desirable due to increased friction and blower speed. Furthermore, the blown motor isn’t as dependent on evenly spaced intake or exhaust pulses for airflow tuning, so it doesn’t need the flat-plane crank’s firing order. Finally, the Voodoo crank is lightly built for rev-ability and isn’t expected to hold on to 1,100 horsepower for an extended period of time. Considering all that, the checkbook was brought to bear on a rather special, billet, 90-degree crank from crank-builder-to-the-stars, Winberg.
What the blower crowd should take interest in the Shelby engine are its block and cylinder heads. Make no mistake the Voodoo block is much stronger than the Coyote and features important detail improvements. Obviously the bore is a little larger for a useful gain in displacement and to support larger intake valves, plus those bores feature the trick plasma transfer wire arc process for unparalleled durability.
This block also features small water passages between the semi-Siamesed bores to aid critical top-of-cylinder cooling while providing strong cylinder structure. Down below trick oil squirters—similar to those used on the Shelby GT500 blocks— keep the pistons cool. They feature a tiny check valve to allow oil cooling only above 50 psi of oil pressure—when the engine is revving and needs the extra cooling. The rest of the time the squirters are closed, lessening the oil mist dragging around the rotating assembly while cruising. There are detail differences in the Voodoo block’s internal water passages for extra cooling as well.
Physically the Voodoo block is more robust than any Coyote. The deck is reinforced and the valley more filled-in to support the bottom of the cylinders, plus the main bearing webbing is beefier. That webbing also features extra draft holes to improve bay-to-bay breathing. This allows that oily windage flow more easily from one pair of cylinders to another and helps ring sealing for more power and less blow-by.
Jim Bell bears strong witness to the Voodoo block’s strength because his superchargers sit atop even more powerful Coyotes in drag applications. Those engines didn’t live until fitted with this block, and now they do.
On the power-building side, the Voodoo cylinder heads are also impossible to beat. Works of industrial art, especially considering they came off an assembly line so tattooed by CNC machines that you must remind yourself they are castings. The entire combustion chamber and every inch of the intake and exhaust ports is CNC-shaped for precision and consistency cylinder-to-cylinder. This is something Ford would love to do with every head they make, but it’s impossible in mass production volumes and thus this treatment is exclusive to this private reserve of special engines.
For this engine all Gil did to the production Voodoo heads was bolt them on the short-block. They are that good. Yes, he did change the valve springs for a bit more pressure and fitted his own set of blower camshafts—using the standard Coyote firing order, of course. As far ports, valve job and combustion chambers go, these heads are stock.
We’ll pause here to reflect that traditionally engine builders spent endless hours practicing their magic by porting the cylinder heads in quest of horsepower. But today the power comes built into the heads thanks to ever-increasing CNC availability, leaving the engine builder more time to develop fuel, spark and valve event strategies, along with detailing the bottom end for longevity.
“It’s not magic,” he says, “just basic engineering.”—Gil Nevarez, Nevarez Racing Products
For example, the lobe centers on these cams are 130 degrees; on a traditional pushrod small-block this would have been more like 110 degrees. Like everything else, Gil says his blower cam specs for the Coyote/RoadRunner/Voodoo engines are a balance of the grind fixed in the cam and the bandwidth allowed by variable cam timing. “It’s not magic,” he says, “just basic engineering.”
The Big Blower
Once the long-block was built by Gil in Las Vegas, Nevada, it was delivered to GTR High Performance, a busy SoCal speed shop and installation center located close enough to hear the blowers whining at Kenne Bell in Rancho Cucamonga, California. There Ken Christley was able to work alongside GTR major domos Ricardo and Gonzalo Topete while mounting the first-ever 4.2 KB blower kit on the “1,100-horsepower” engine.
As Ken—who designs all this stuff at Kenne Bell—pointed out, the 4.2 kit is a development of the now-familiar 3.6-liter KB kit for late-model Mustang GTs. The 4.2 blower itself is simply a little longer than the 3.6, but is otherwise the same diameter and height. The intake manifold is unchanged.
Because the rear of the 4.2 case is longer, it forced a change to the fuel rail crossover at the rear of the engine. The 3.6 blower uses the stock factory rails—they can easily support huge blower power as can most of the stock late-model Mustang fuel system—but the 4.2 requires a new crossover at the rear of the engine to clear the blower.
…We have the biggest of everything—Jim Bell, Kenne Bell
And, the 4.2 requires a serious belt. Referencing his entire line of superchargers, Jim Bell says drive loads range from just less than 100 horsepower for the smallest blowers to 400 horsepower when making the 1,700-plus-horsepower stuff whine. That’ll definitely make your six-rib squeal.
Large drive loads also demand stout brackets, lengthy belt wrap and healthy spring tensioners to avoid distorting under moments of high supercharger load, and Kenne Bell has that covered. Unexpected, however, were the struggles of retaining the alternator in mega-power applications such as this. Belt tension gets so great under blower loads, the alternator flexes out of alignment. Kenne Bell tried a reinforcing brace at the front of the alternator, and this held the alternator square, but the loads then pass into the alternator body and crack it!
Ultimately, the best solution was isolating the alternator from all the crazy loads in the blower belt by fitting a second belt dedicated just to driving the alternator. The 4.2 kit is the two-belt solution’s market debut but it’s already been proven in custom drag-racing applications.
At our deadline the 1,100-horsepower engine was being strapped to the engine hoist for the big drop into the 2017 Mustang chassis. Jim Bell “positively guarantees” it will make 950 horsepower at the tires—and we’ll be there when it does, so stay tuned.