If you watch automotive television, you no doubt saw this Shelby GT350R receive a Hellion turbo system and put down 723 horsepower and 654 lb-ft of torque on just 9 pounds of boost. It was a great start, but car owner Jim Guthrie wanted to turn up the boost and make over four-digit horsepower. To do so meant upgrading the engine to handle more boost.
“We knew that the GT350 platform would be very similar to our GT system, so the answer was not if, but when we would make the adaptation,” John Urist of Hellion Power Systems explained. “We already have had amazing results with our record setting GT kit, so we knew we could push the Voodoo engine.”
How do you push a Shelby GT350R to four-digit horsepower? With upgraded internals and an off-the-shelf Hellion twin-turbo system! (Photo Credit: Hellion)
Suited for Voodoo
Based on those initial results, the kit definitely works well on the Shelby GT350. Obviously John is a believer in turbos, but in this case he believes his system is particularly suited for the Shelby’s 5.2-liter engine.
A turbo system will not pull on the front of the exotic Flat-Plane Crank.—John Urist, Hellion
“With a turbo system being the most efficient power adder already, there was another advantage. A turbo system will not pull on the front of the exotic flat-plane crank,” John said. “With the balance challenges already inherent in the Voodoo engine, its that much more important to not change the dynamics of the engine by pulling on the front snout.”
While the GT350 system is similar to its Mustang GT cousin, John did have to use the latter system as a basis to create a new, Shelby-specific twin-turbo system.
Most people don’t consider that the valve springs have to work against the boost pressure in the chamber to open the valves. John knows a thing or two about building boosted engines, so he replaced the stock valve springs (right) with the upgraded units from Modular Motorsports Racing, which are roughly 15 percent stiffer than the stockers. “We also upgraded the valve springs with MMR titanium retainers and springs. We upgrade valve springs in high-boost applications,” John said. “In addition, we upgraded the oil pump gears and bottom chain sprocket with MMR high-strength units.”
“We had to change a few pipes in the kit to adapt to the amazing factory headers that our kit retains,” John said. “The design and fitment remains ergonomic and clean. The proper component position and routing is the same as our GT kit, and connects to the factory exhaust.”
The first car to receive this kit was owned by a local racer, who offered up the car as a showcase for the kit’s television debut. Because he is such a good customer, John offered to fortify the car’s engine, reinstall the kit and tune it up for big power. To do so, of course, he would need more robust engine parts, so he turned to his supporters for some custom pieces.
The Voodoo 5.2-liter features a different firing order than its cousin the Coyote thanks to its flat-plane crankshaft. That means its cams are unique to the Voodoo engine. John removed them to swap springs, but John says the factory grinds are great for all-around performance, so they remained in the engine.
Built Boost Tough
“This beautiful GT350R is owned by racer Jim Guthrie here in Albuquerque, New Mexico. We have already made amazing power with this car in stock form, but it was time to take it to the next level,” John told us. “Jim and I decided to order custom pistons from Arias, and custom rods from Carrillo to replace the factory units. With an engine like this, these are the two weakest links.”
While many might find it daunting to open up a Voodoo engine, John has long built his own racing engines, so he was game for the challenge. He did want to approach the upgrade like a regular guy would, so he left the crank in place and added direct-replacement upgrades where they were absolutely necessary.
Built for free-revving high rpm, the Voodoo 5.2-liter engine is born with lightweight forged pistons featuring an anti-friction skirt coating. John opted to replace these with a set of custom billet beauties from his sponsor Arias. These rugged pistons match the dimensions and weight of the factory slugs while offering boost-friendly durability. John blueprinted the engine parts before assembly by measuring every part to ensure the pieces were all perfect.
With a upgraded rotating assembly, this engine will now be able to handle well over 1,000 rear-wheel horsepower.—John Urist, Hellion
“The pistons and rods were made to the exact weights as the factory parts, thus keeping the balance to factory specs. Ford spent the time to set the desired balance of the rotating assembly, and we wanted to keep it the same,” John added. “With a upgraded rotating assembly, this engine will now be able to handle well over 1,000 rear-wheel horsepower, which is where we want to take this R!”
While John spec’d out custom bits from Arias and Carrillo to fill the block, he opted to leave the factory 5.2 block untouched.
“We decided to leave the block untouched with the factory spray-bore lining. In our experience this finish is reliable to 1,000 horsepower,” John explained. “When we go over 1,000 rear-wheel horsepower, we recommend having Modular Motorsports Racing sleeve the block with high-horsepower sleeves. MMR builds our high-horsepower engines such as Melissa’s record-setting 2015 GT engine.”
Balancing weight and high-rpm durability, the stock Voodoo rods (far right) are forged steel with a fracture-split cap. John replaced these with a stout set of custom Carrillo H-beam forgings built to withstand up to 2,000 horsepower. Amazingly, this new rod and piston combo is the same weight as the factory setup, so no balancing of the flat-plane crank was required.
The Supporting Cast
Once the new engine was built, John installed a McLeod RXT clutch and reinstalled the turbo system. A big-power combination was ready to roar, but it would need more fuel than the factory system was designed to support. Amazingly, the solution for four-digit horsepower was simply a set of larger injectors and a fuel pump voltage booster designed for the GT350’s stock dual-pump system. He topped it off with a custom calibration built using HP Tuners gear.
“The initial calibration that we send in our system is capable of handling this power increase with only the JMS dual-pump FuelMax to boost fuel supply, which is very critical in applications over 750 rear-wheel horsepower with our 95 lb/hr injector upgrade.” John said.
Not wanting to tamper with the artfully constructed Voodoo block, John opted to leave the Plasma Transfer Wire Arc cylinder lining in place rather than sleeving the block. Having spec’d the pistons to precisely match the stockers; he simply reassembled the engine with the new parts. John believes that the factory gaskets are the best solution at this boost level, so he used a fresh set here.
The Mustang GT System
As we mentioned in the main story, Hellion Power Systems also offers an Eliminator Twin-Turbo system for the 2015+ Mustang GT. This kit comes standard with the same vertical-flow, dual-inlet intercooler; TurboSmart VEE Port bypass valves and 55mm turbos as the GT350 kit and it will deliver similar performance results assuming the car has the engine mods and support systems to feed four-digit horsepower.
With the new built, boosted and fueled combo in place, the turbo Voodoo engine exceeded the expectations that Jim had in mind. Not only did it blast out over 1,000 rear-wheel horsepower, but it put down four-digits worth of torque. Being the 5.2-liter engine doesn’t have a rep for being a torque monster, so these numbers are all the more impressive.
“With the technology advancing at an all-time high, these Precision 55mm units make the power of older 62mm units with an increased spool time,” John concluded. “The crushing torque that the Hellion kit provides really wakes up the lack of low-end power that the GT350 is known for. This is due to the quick response of the 55mm turbos.”
“In addition to the engine upgrades, we installed a state-of-the-art McLeod clutch to help handle the extra power and torque,” John said. “It is a bolt-in unit and is easy to install.” Knowing the goal was exceeding 1,000 rear-wheel horsepower, he installed the RXT twin-disc clutch (PN 6337807M).
Built specifically for the Shelby GT350, these clutches will corral up to 1,000 horsepower with streetable pedal effort.
If you want even greater power and are willing to fortify the engine even more by adding block sleeves, you could always add Hellion’s optional turbos and really go deep into the four-digit range.
Here is the completed installation. With a few slight tweaks Hellion was able to create a twin-turbo system specifically for the latest Shelby GT350/GT350R. It bolts on with no cutting, so you could return your rare rocket to stock down the road.
“We have made 1,160 rear-wheel horsepower with the twin 55 turbos on conventional 90-degree-crank cars, so we do not see any reason that is not attainable with the Voodoo engine,” John added. “We have a couple options for larger turbos if over 1,500 horsepower is desired.”
John knew that the factory fuel system would hit the wall well before this car reached its full potential. As such, he added a set of 95 lb/hr fuel injectors and supported those with a GT350-specific JMS FuelMax pump voltage booster (PN P2020PPS15; $599), which increases the output of the factory dual pumps by up to 85 percent and supports over 1,000 rear-wheel horsepower. John attached it to the factory tire-inflation kit so as not to blemish the GT350 chassis.
Ford may have never intended for the Shelby GT350 to see boost, but the Voodoo 5.2-liter engine sure seems to love 18 psi or so as long as it has the proper supporting gear. If you are willing to run 9 or so pounds, you don’t need to fortify the engine and the performance is still pretty impressive. Either way, you’ll have one of the most fun cars on the road.
To find out what kind of power a built Voodoo 5.2 with two turbos can put down at the rear wheels, John took the car to The Dyno Edge in Albuquerque, New Mexico, to run the car on a Dynojet chassis dyno. Ready for big boost Jim Guthrie’s built Shelby GT350R more than doubled its output with the addition of a Hellion Eliminator twin-turbo system. Where Most GT350s put down mid-to-high 400s in horsepower and high 300s in torque, this car rocked the rollers with over 1,000 horsepower and 1,000 lb-ft of torque at the wheels. Jim will have no complaints about bottom-end torque with this car!