Road & Track, in its December 2001 issue, had some interesting things to say about the 6.4 engine:
"The 6.4 Hemi's cast-iron 90-degree V-8 block was bored by 0.9mm and its newly fillet-rolled and micro-alloyed forged steel crank stroked by 3.5mm. The aluminum heads retain their unique twin sparkplugs, but gain cylinder deactivation. Forged aluminum pistons carry rings that reduce friction and are cooled by oil squirters. Oil is routed to rhe cast-aluminum oilpan with crank scrapers and kept there with a windage tray before being sucked up and passed through an oil cooler.
The new design allows for increased compression- now 10.9:1. The heads are cast with fine core sand that results in a surface finish that negates the need for port polishing. Variable cam timing is new to the big Hemi and tuned to provide optimal power and efficiency depending on engine load. Air flows around fantastically large hollow stem 54.3mm intake valves at 18 degrees and out around sodium-filed 42.0mm exhaust valves at 16.5 degrees. The resultant hot exhaust is routed through a stainless steel header and then to a 2 3/4 inch exhaust that uses an active valve to control sound emitted when the cylinder deactivation kicks to a 4-cylinder mode. The switchover is easily discerned by the driver, not bu sound but by a green ECO light displayed on the dash. It's hardly noticeable in any sense when it switches, and generally the exhaust is muted to an acceptable rumble, but dig deep with the right foot and a righteous V-8 roar emits."