New Member
Established Member
Oct 18, 2011
Lakeland, FL

Breathe Deep
Kooks unlocks the potential of the Voodoo 5.2-liter engine with full exhaust
By Steve Turner
Photos by Steve Turner and courtesy of Joe Charles

There is little doubt that the 5.2-liter Voodoo engine in the latest Shelby GT350 exhales with the best exhaust sound of any factory Mustang. This is especially true of the resonator-free R-model with its exhaust valves in the open position. Yet with all the airflow scurrying through the engine at 8,250 rpm, we had to wonder if long-tube headers and a freer-flowing exhaust would unleash even more power from this flat-plane-crank V-8.

Recently the exhaust experts at Kooks let out a teaser video of the company’s freshly minted 1 3/4- to 1 7/8-inch Step Headers, a pair of 3-inch Front Connection Pipes with Green Cats, and a 3-inch X-pipe mated to the factory axle-back and mufflers. They followed that up by rounding out the system with one of the company’s own axle-back systems featuring Kooks mufflers.

While Kooks prototyped this system using a race car, a street-going GT350 was needed for the initial test fitment and dyno testing. That’s where Hi-Po Joe Charles came into the picture. While he has a long history of racing with the NMRA and running Kooks exhaust gear, Joe recently sold his Coyote Stock machine to make way for a new, Triple Yellow Shelby GT350. The car wasn’t in his garage long before he dropped it off at Kooks headquarters in Statesville, North Carolina.

“I lack the ability to leave well enough alone. It was only natural that I choose Kooks Custom Headers & Exhaust to upgrade the factory exhaust on my Shelby,” Joe explained. “The OEM exhaust sounds amazing from the factory, but I was looking for more power. I have worked closely with Kooks for the last four years with exhaust system upgrades for the Coyote Stock car and I knew they’d be able to make a better functioning exhaust.”

It turns out that Joe was on to something, as his car baselined at 466.72 horsepower and 390.19 lb-ft of torque on the Dynojet chassis dyno at Roush-Yates Racing in Mooresville, North Carolina. With just the addition of the Kooks headers, cats, and full exhaust, the peak horsepower jumped to 491.02 and torque climbed to 410.01 lb-ft at the wheels. Kooks even compared the stock mufflers versus its upgraded cans an found the mufflers alone were worth nearly 10 horsepower. Better yet the torque improved, which helps overcome the car’s inherently soggy output down low and should really improve its driveability—and that’s before tuning!

“I was very impressed with the results after adding Kooks exhaust. The sound of this engine is very unique and the new exhaust makes it sound that much better,” Joe said. “As soon as I get the car back it is going to MV Performance in Statham, Georgia, for a custom tune. I will add a JLT cold-air intake and then Tim Matherly will be tuning the car for maximum performance with the HP Tuners nGauge. It is possible that we will also make a file for E85 fuel. If we have time, I plan to run the car at a quarter-mile track to see what it will run on street tires.”

Running the car at the drag strip isn’t all he has planned for the car. Joe wants to experience his deep-breathing GT350 with his foot to the floor for an extended period of time.

“The weekend of January 23 and 24 I will be attending the wannaGOFAST half-mile race in Ocala, Florida,” Joe added. “I’m not sure what to expect, but our goal will be 142-145 mph.”

The car should sound amazing at that speed with this exhaust system.


True long-tube headers and a full exhaust definitely help the Voodoo 5.2-liter engine breathe. Not only did peak horsepower improve by more than 24 horsepower, but the bottom-end torque really improved. This should give the GT350 the kind of around-town grunt it’s been missing.


The Kooks Shelby GT350 headers feature a stepped design where the tubing increases in size from 1 3/4 to 1 7/8 inches before terminating at the collector.


For those that aren’t huge fans of the higher pitch of the FPC 5.2’s exhaust note, the Kooks mufflers return some of that all-American rumble to the exhaust.


Joe’s GT350 baselined at 466.72 horsepower and 390.19 lb-ft of torque at the rear wheels on the Dynojet at Roush Yates. Adding the Kooks long-tubes, Kooks Green cats, and Kooks mid-pipe but sticking with the stock mufflers raised the output by 15.14 horsepower and 16.47 lb-ft. Stepping up to the Kooks axle-back and mufflers tacked on another 9.16 horsepower and 3.35 lb-ft for total gains of 24.3 horsepower and 19.82 lb-ft over the baseline. That’s impressive for adding just the exhaust and leaving the stock calibration in place.


Active Member
Established Member
Jul 25, 2009

Hopefully they pull the cats off and do a tune to it.

I think full exhaust, intake and tune you'll see around 525whp on these cars. Give or take some. Deleting the cats will free up some power for sure


Well-Known Member
Established Member
SVTP OG 4 Life
Feb 15, 2008
Great gains. Congrats to the op/owner. Very cool. Sound is awesome.

-tuning will be worth at least 25whp more IMO. ~50whp from exhaust and tuning is exceptional for an na vehicle.

-this yellow screamer might be one of the first gt350's to break 525whp, maybe even 550whp if they go e85, cai, etc etc.

I'm curious when a race application will break 600whp na... I'd imagine aggressive cams, minor head assessments, e85, the aforementioned bolt ons, and a few special considerations like colder plugs gapped well, amsoil, excellent air conditions, etc might get a voodoo into hci c6z whp territory. 550-600whp...

That's insane considering one engine is 105ci smaller than the other....I'm rambling but it could happen.

Users who are viewing this thread