Jeep Grand Cherokee SRT8 HPE800 by Hennessey Performance Engineering
Name: Hennessey HPE800 Jeep SRT8
Based On: Jeep Grand Cherokee SRT8
Stock Power: 420 horsepower, 420 pound-feet
Tuned Power: 800 horsepower, 770 pound-feet
Jeep is typically known for producing vehicles with tremendous off-road capability. At the 2005 New York International Auto Show, however, Jeep showed the Grand Cherokee SRT8 that threw most of its storied off-road heritage out the window in favor of hardcore street performance. And almost since the beginning, Hennessey Performance Engineering has been turning out more powerful SRT8s.
Hennessey produces six different variations of its modified SRT8 ranging from 475 to 800 horsepower. In the spirit of excess, we're going to concentrate on the latter. Hennessey starts with a relatively tame Grand Cherokee SRT8 that puts out 420 horsepower and 420 pound-feet of torque from a 6.1-liter V-8. From there, Hennessey adds a 426-cubic-inch Hemi stroker kit to increase displacement to just under 7.0 liters. Included in that kit are a new 426 stroker crankshaft, forged aluminum pistons, and forged steel connecting rods. The kit helps to strengthen the engine and, along with a performance valve job, lower the compression ratio in preparation for adding twin-turbochargers. An air-to-air intercooler is added as well.
Further modifications include beefed-up transmission internals to prevent grenading, upgraded fuel injectors, engine management software, and a three-inch dual exhaust. All of these modifications are good for a total of 800 horsepower and 770 pound-feet of torque. Hennessey doesn't list performance numbers for its range-topping HPE800, but its lesser HPE600 sibling will do 0 to 60 mph in 3.8 seconds and blaze through the quarter-mile in 11.9 seconds at 121 mph. We can only imagine the HPE800 is a bit faster.
As with all of Hennessey's products, it's covered and guaranteed. Hennessey dynos all of its vehicles to guarantee an accurate power rating and runs each down its private quarter-mile test track in Texas. The Grand Cherokee SRT8 HPE800 is covered by a full, one-year limited warranty.