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.
Kooks Custom Headers PN6920 (headers) and cat pipes PN1002741 are constructed from 304 sta
Before attempting to remove the OEM exhaust manifold, Mike had to remove the frame crossme
After removing the passenger side exhaust manifold bolts, Mike was able to remove the OEM
Peering up into the engine compartment from underneath, we could see how tight the 6.1L V-
This comparo shot gives us a good idea of the design difference between the OEM manifold (
Mike carefully maneuvered the Kooks header up into position.
The Percy's High Performance 3/8-inch thick carbon material header gasket was then sandwic
Mike installed the Kooks high-flow cat pipes that linked the headers to the factory muffle
A worm's-eye view let us admire the complete Kooks stainless steel header/crossover exhaus
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
Pneumatic wrench, ratchet, and assorted socket sizes
Kooks Headers PN6920 $1,158.74
Kooks High Flow Cat Pipes PN1002741 $746.75
(All prices from Kooks Custom Headers and do not include labor or other material cost)