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.
Destined for a special Hurst-Kenne Bell Mustang, the 1,100 hp engine was already wearing its distinctive gold coil covers when the 10-rib blower drive was mocked up.
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.
Durability is the main attraction of the Winberg crankshaft, but it’s also a beauty to look at. Aero-shaped counterweights are a Winberg development and just one detail in this highly featured crank. This shaft is said to be good to 2,000 horsepower and 10,000 rpm. While a nicely featured production crank, the 180-degree Voodoo shaft (left) is visibly optimized for lightweight rev-ability—not boost. Both crankshafts are identical except the smaller rod journal diameter—2.005 inches versus the stock 2.086 inches—specified by Gil Nevarez for this application. It’s obvious in person, but in photos seeing the 180-degree physique of the Voodoo crank (left) versus its 90-degree Winberg replacement is best done head on. Check out the wall thickness of the Winberg’s snout. Large, 0.125-inch radii; a beefcake snout to survive blower drive belt loads; lightning holes in both main and rod journals; heavy metal balancing inserts; and aero profiling show this crankshaft has it going on. Not visible is Winberg’s dedication to using only top-quality steel billets.
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.
Just in case you might not notice a locomotive rolling over your toes, this is definitely not a low-buck project. Every part in this build is premium, some of it, such as the billet crankshaft, not even available to the average Joe no matter how much money you wave around. How do you even get a Voodoo production engine anyway?
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).
Gil Nevarez selected billet 4340 Oliver connecting rods, but needed the lightened version because he couldn’t get enough counterweight on the crankshaft to offset Oliver’s heavier units. It’s a compromise driven by the compact crankcase dimensions of Ford’s modular V-8s. Length checks in at 5.850 inches. From left is a stock 5.0 Coyote rod/piston, followed by a stock 5.2 Voodoo and the Oliver/Manley combo from the 1,100-horsepower engine. It’s pretty obvious where the rod muscle is in this lineup; a closer look will show the 1100’s forged piston is thick as brick, sports an abutment-like pin boss and much greater thrust surface.
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.
Compression in the 1,100-horsepower engine was unspecified, but clearly low and blower-friendly with the expected flat top for unhindered flame front travel. Forged from 2618 aluminum by Manley, these heavy blower pistons are hard anodized with a moly coating over the anodizing on the skirt. Piston diameter clocks in at 3.704 inches. Peeking under the Manley’s skirt is another reminder blower engines don’t skimp on piston strength, and you can bet the crown is thick as a bank vault. Gil notes that NASCAR engines have gone to nickel-coated pistons for durability, which is something he’d like in high-power blower engines to allow tighter ring groove clearances and thus reduced ring flutter. You’d expect an 8,200 rpm engine to wear super-light, thin rings and the Voodoo example at left doesn’t disappoint. The 1,100 engine’s ring pack next door measures a typical 1.5 x 1.5 x 3.0mm and features a heat resistant steel upper ring, a ductile-iron second ring and a high-tension, Hasting’s style oil ring. The upper ring is critical; it’s a bit beefy and carries no moly coating because moly flakes off dangerously should the engine detonate. Ring flutter is an issue with both engines, hence the buffer groove between the top and second rings on both pistons.
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.
Voodoo oiling beats Coyote oiling, and the 1100-horsepower engine uses the Voodoo’s oil pan and beefier oil pump. The pan is actually an assembly of pan, pan gasket, oil pump pickup and windage tray that does not separate after assembly by Ford. Plastic as Los Angeles culture, even the pan’s drain plug is composite. Best keep this one off curbs and don’t even think of wheel standing it. Another nod to the Voodoo’s 8,200 rpm-character is the tighter-fitting windage tray featuring these taller scoops that capture drain-back oil. They’re just as useful in the blower engine. We also noticed the Voodoo pan lacks an oil level sending unit boss.
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.
The Coyote oil pump (left) is easily identifiable by the two-bolt boss for the pickup tube. The Voodoo pump at right uses a rubber socket instead. The Voodoo inlet is also larger—1.250 vs. 1.0 inches—and boasts billet gears instead of the Coyote’s cast gerotor set.
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.
Excellent right from Ford, the stock Voodoo multi-layer head gasket is carrying over to the 1,100-horsepower engine. Clearly wanting plenty of clamping force, Gil reached for industry standard ARP studs, nuts and washers for cylinder head retention duty.
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.
There’s nothing more amazing in this 1,100-horsepower engine than stock Voodoo cylinder heads. Obviously Ford did its homework when CNC profiling the chambers and ports in these castings. Voodoo heads use a slightly wider valve spread and larger valves than Coyotes. The resulting 38.3mm x 32.5mm diameter package also employs hollow-stem intake and sodium-filled exhaust valves. The latter must be especially useful on a blower engine. Both the intake and exhaust ports on the Voodoo heads show the same wide registration lines whittled by the CNC cutter. While it looks and feels harmful to airflow, much previous experience proves it isn’t. You can polish them smooth if you want, but you’ll still only get 1,100 horsepower…
“It’s not magic,” he says, “just basic engineering.”—Gil Nevarez, Nevarez Racing Products
Going back to the camshafts, Gil noted the return to a 90-degree crankshaft saved him considerable development on this engine because he was able to use grinds he developed during the 5.4-liter GT500 Shelby 1000 program. He says these cams are worth 45 horsepower over the stockers, a gain realized only after considering not only the traditional lift, duration, overlap ground into the cam lobes, but also how those specifications interact with the twin independent variable cam timing on the modern Four-Valves such as the Voodoo and Coyote.
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.”
Held in reserve so far on the 1,100-horsepower Hurst/KB engine, Kenne Bell carries this new high-strength billet belt tensioner from American Racing Solutions. Stock Coyote tensioners are easily good to 800 horsepower and standard Kenne Bell fitment is the 1,000-horsepower-worthy Shelby GT500 tensioner in the background, but the ARS piece may prove useful on mega-power engines with 10-rib drives, big boost and jazzy drivers. We didn’t have time to arrange the bazillion nuts and bolts that go with these major parts of the Kenne Bell belt drive, but you get the idea. There are plenty of pieces, but they’re easy bolt-ons and the instruction manual is wonderfully detailed. Here are the key parts of the new 10-rib drive: the twin-sheave pulley with both 10-rib and four-rib sections in the foreground, the four-rib alternator pulley, skinny four-rib belt and tensioner.
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.
Kenne Bell superchargers use water-to-air charge cooling, so the usual two heat exchangers, pump and reservoir are required—plus a few more nuts and bolts we elected not to clutter the photo with. This radiator mounts behind the bumper; the other heat exchanger is in the intake manifold.
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
A new 10-rib belt drive was developed for the 4.2 blower. Jim Bell admits the 10-rib is far more belt than his blower kit needs in casual street driving, but guys with 4.2 blowers are not casual and even though they often start out with a mere 750 horsepower or so at the tires, are an easily jaded bunch that almost always comes back for more once the new wears off. Instead of forcing everybody through an involved front engine dress rebuild when stepping up its game, Kenne Bell is going all the way with the blower drive out-of-the-box with the 4.2’s.
Jim Bell “likes to show we have the biggest of everything,” and here’s some downspout engineering as evidence. That’s a 5-inch inlet tube—chromed, of course—in back and the giant oval throttle body. We could tell you the KB Mammoth oval throttle body is so many millimeters or simply prop a quarter up in the bore. Believe it or not, the company actually has an even larger throttle body with twin 105mm blades. It mounts at the rear of the blower and aspirates through the car’s cowl so it’s for 1,700-horsepower drag racers.
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!
Kenne Bell’s standard Mustang intake manifold and charge cooler has plenty of capacity for 1,000-plus-horsepower engines. At this power level all KB blowers and manifolds are polished. Kenne Bell’s 4.2-liter supercharger uses a 4x6 rotor profile, meaning it uses a four-lobe female rotor and six-lobe male rotor, which is said to offer greater efficiency than the 3x5 rotors in blowers from other manufacturers. All 4.2s are liquid cooled around the front bearings and wear the enlarged, curved Mammoth inlet.
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.
Ricardo mocked up the 1,100 short-block with the blower and belt drive before it went into the Mustang chassis. Here he already fitted the 5.0 water pump, ATI damper from the Kenne Bell kit and is installing the drive system’s bracket. This two-pulley idler and the tensioner below it bolt to the big drive bracket. This is all easy wrench work, but it’s nice to have a helper to read instructions, hold the belt in place and help sort out the numerous pulleys, stand-offs, bolts, spacers and so on. Then Ricardo fit the two-sheave idler; it fits just above one of several 10-rib idler pulleys installed previously. Both the 10-rib blower belt and four-rib alternator belt are visible here. Their common point is the pulley at 4 o’clock to the water pump pulley. Both belts have their own tensioners; the alternator’s is manual, the 10-rib is spring-loaded.
Ricardo Topete lowers the intake manifold while Ken Christley stands ready with bolts. Normally this step is done with the engine in the car to save weight and avoid blemishing the blower with engine hoist tackle. Gonzolo (left) helps his brother Ricardo lower the 4.2 onto the intake. The supercharger is approximately 65 pounds, so a helper is an excellent idea for this step.
When you make this much power you can boast a little on the blower-drive pulley. All of the 4.2-liter Kenne Bell kits come with this pulley, which like all KB pulleys, is easy to change should different boost be desired at the track and street.