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The 425-horsepower, normally
aspirated 6.1-liter HEMI is the highest specific-output V-8
engine ever offered by the Chrysler Group. Its 69.8
horsepower-per-liter rating exceeds even that of the
legendary 1966 "Street HEMI." Torque is rated at 420 lb.-ft.
Although the Chrysler HEMI was born in the 1950s and entered
into legend in the 1960s and '70s, today's version took much
of its inspiration from the original - particularly the
namesake hemispherical combustion chambers that provide
power and efficiency. |
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When SRT set out to develop a
more powerful HEMI for the Chrysler 300C SRT8, they were
mindful of the engine's heritage, which led to adopting
traditional HEMI engine cues, such as an orange-painted
cylinder block and black valve covers.
The SRT powertrain engineers who developed the Chrysler 300C
SRT8's engine achieved more horsepower by adding more cubic
inches, increasing the compression ratio, redesigning the
cylinder head intake and exhaust systems for increased flow,
and increasing engine speed.
To get more displacement, SRT engineers bored out the
diameter of the cylinders in the Chrysler 300C SRT8's HEMI
by 3.5 millimeters each, 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, unleashing more energy in
the combustion process.
Engine breathing was increased with new high-flow cylinder
heads, a specially designed intake manifold, and exhaust
"headers" with individual tubes encased in a stainless steel
shell, all unique to the 2005 Chrysler 300C SRT8's 6.1-liter
HEMI engine. Larger diameter valves and reshaped cylinder
ports in the heads allow for maximized air flow. The intake
manifold was designed with larger diameter runners for
higher-speed tuning. Exhaust is routed through a
larger-diameter (2.75-inch vs. 2.5-inch) exhaust system with
3.5-inch chrome tips.
Performance-oriented camshaft profiles were developed to
balance total vehicle requirements, simultaneously allowing
more air in and out of cylinders. This increases performance
and manages a higher engine speed, which is another method
to increase horsepower. SRT engineers increased the HEMI's
peak engine speed nearly 15 percent, to 6,200 revolutions
power minute (rpm) from 5,400 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 6.1-liter HEMI is further strengthened
with a host of redesigned components, including a reinforced
engine block with increased coolant flow, forged steel
crankshaft, high-strength powdered-metal connecting rods,
floating-pin pistons (cooled by oil squirters), and an oil
pan modified for reduced oil foaming.
The 6.1-liter HEMI's power is channeled through an A580
five-speed automatic transmission with specially calibrated
AutoStick® driver-selectable range control, which offers
fully automatic or manual shifting selection. A heavy-duty
four-flange prop shaft sends the torque from the
transmission to an upgraded differential and axles. |
