The 6.1L-liter V8 HEMI made its Jeep debut in the 2006 Grand Cherokee SRT8 which went on sale in January of 2006. When SRT powertrain engineers set out to develop a more powerful HEMI they were mindful of the engine's heritage, which led to adopting traditional HEMI engine cues including an orange-painted cylinder block and black valve covers. SRT engineers who developed the 6.1L engine achieved more horsepower by adding more cubic inches, increasing the compression ratio, and redesigning the cylinder head, intake and exhaust systems for better flow and increased engine speed.

For more displacement, SRT engineers bored out the diameter of the cylinders in the HEMI by 3.5 millimeters each in order to increase the total displacement to 6.1 liters from 5.7 liters. Compression ratio was also increased to 10.3:1 from 9.6:1, increasing engine efficiency and power. Cylinders are honed with torque plates to ensure a truer bore, to reduce friction and increase power.

Engine breathing was increased with new higher-flow cylinder heads, a specially designed intake manifold, and exhaust headers with individual tubes encased in a stainless steel shell, all unique to the 6.1-liter HEMI engine. Larger-diameter valves and reshaped ports in the heads allow for maximized air flow. The intake manifold was designed with larger diameter and shorter runners for higher-speed tuning. Exhaust runners allow increased gas flow while maintaining fast catalyst light-off, while adding 12 horsepower over the 5.7-liter engine’s cast manifolds. Exhaust is routed through a large diameter (2.75-inch vs. 2.5-inch) exhaust system with 3.5-inch chrome tips.

To further increase horsepower, performance-oriented camshaft profiles were developed to allow more air in and out of the cylinders, as well as manage a higher engine speed. A billet steel, high-strength camshaft features more overlap and lift for better performance. Silent chain, 5-bearings. Bi-metal material except number 3 Babbit. Deep-fillet rolled journals for improved fatigue life, press fit damper to minimize torsional vibration.

SRT engineers increased the HEMI's peak power output engine speed by nearly 20 percent to 6,000 revolutions per minute (rpm) from 5,000 rpm. Intake and exhaust valve stems are hollow, and the exhaust valve stems are filled with sodium to help dissipate heat more efficiently.

The high-performance SRT 6.1-liter HEMI is strengthened with redesigned components, including a reinforced engine block, forged micro-alloy steel crankshaft with retuned damper, high-strength powdered metal connecting rods and floating-pin pistons. The pistons are cooled by oil squirters, aimed at the underside of each piston to aid piston cooling for engine durability. A special oil pump pressure relief valve is added to accommodate the squirter oil flow. The oil pan and windage tray are modified to manage oil return to the pan sump at high engine speeds and improve power.