When people bolt-on headers to their vehicle's engine, their main satisfaction is the throaty sound they produce. Sure the sound is impressive, but more importantly from a performance aspect, the headers will improve the engine's throttle response, torque, hp, and fuel mileage.

What makes the OEM exhaust manifold and header swap such a noticeable improvement is the header's inner diameter and the equal length tubes. These two factors affect the burnt gasses flow rate, or velocity, as the gasses exit the exhaust ports of the cylinder heads and are propelled by the compression release of each of the exhaust ports, known as pulses. The headers increase the velocity of the burnt gases as they travel through the exhaust system, thus increasing both torque and horsepower.

The '08 Jeep Grand Cherokee SRT-8 is a real beast from the factory with its 6.1L Hemi V-8 producing 420 lb-ft of torque and 420 hp. With AWD and that much power on tap, the SRT-8 launches like a dragster, but like all gearheads, more power is always better. To increase the mighty SRT-8's grunt, we decided to bolt on a set of Kooks Custom Headers and high-flow pipes that connect the headers to the factory catalytic converters. These Kooks power tubes, when combined with Kooks' high-flow cat pipes, have been dyno-proven to increase the engine performance by 28 hp. That's a huge increase in bolt-on power and the better-breathing 6.1L also sounds like a street-ready assassin.

We delivered the Grand Cherokee SRT-8 to Traders Sport Truck, in Santa Fe Springs, California, where Mike Bogart, Traders' technician specialist, installed the Kooks Custom Headers and high-flow cat pipes.

From The Driver Seat
Before installing the Kooks Custom Headers, we took the Jeep Cherokee SRT-8 for a quick spin. The torque and power was incredible, as the AWD made the SRT-8 handle like it was on rails. After installing the Kooks headers and cat pipes, the second go around was very impressive. The 28- horsepower gain was definitely noticeable from the instant the loud pedal was mashed. I was instantly planted into my seat as the torque and power band came on until my foot was lifted from the throttle. Any occupants with heart conditions might want to stay clear of this Hemi rocket.

Your Questions Answered

Time Spent Working: 3 hours
Degree of Difficulty: Beginner/Intermediate

Tools Used:
Pneumatic wrench, ratchet, and assorted socket sizes

Parts Used:
Kooks Headers PN6920 $1,158.74
Kooks High Flow Cat Pipes PN1002741 $746.75

Total: $1,905.50
(All prices from Kooks Custom Headers and do not include labor or other material cost)

Kooks Custom Headers
141 Advantage Place
NC  28677
Traders Truck Accessories
10242 Norwalk Blvd
Santa Fe Springs
CA  90670
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