C-PLUS-PLUS; Hotter hardware reprograms the Chrysler 300C SRT-8.(News)

Byline: KEVIN A. WILSON

When the first Chrysler 300 was built in the 1950s the appendage of a letter to its numeric name denoted the gentleman's performance sedan, the one with the high-output engine and attendant upgrades. Today, too, the 300C is the 300 with the Hemi and the hefty 340-hp output. But it turns out the new C won't be the 300 with the biggest mojo. That role is reserved for the 300C SRT-8, the big bruiser super-tuned by the boffins at the company's in-house Street and Racing Technology Group. Chrysler is previewing the car at Pebble Beach during the annual weekend of automotive overkill, and must think it has something special on its hands to imagine it can punch through the four-wheeled saturation of the masses at Monterey, who will be inundated with-just for starters-an extensive celebration of Ferrari's 50 years in America.

The 300C SRT-8 should garner a little attention from the bedazzled patrons of the big show, if for no other reason than this: Under the hood breathes a beefed-up and bored-out Hemi V8 packing a 425-hp wallop from 6.1 liters. The thrust-making machine is even decked out with an orange-painted block and black cylinder heads, just like the legendary Hemis of old, some of which are frequent travelers to Laguna Seca and the Monterey Historics, under the hoods of not only Chryslers, but also cars like Cunning-hams and Allards. Both were pretty good at challenging Ferraris back in the day.

Squeezing roughly 70 hp from every liter of displacement makes the SRT Hemi the highest specific-output naturally aspirated V8 ever offered by the Chrysler Group. Sure, 70 hp per liter is about what Toyota gets out of a 3.0-liter V6 in the Camry, but we're talking about pushrod two-valve Detroit iron here, so Dan Knott, director of SRT, is right to brag on his achievement. The handful of engineers working in his shop, hidden away in an industrial park on the other side of the freeway from the Chrysler Technology Center and HQ in Auburn Hills, Michigan, includes a lot of hard-core black-cuticle enthusiasts who tune their own performance cars in their off-hours, of which they've had very few lately.

"I've got engineers who road-race and slalom and set land-speed records,'' Knott points out as we walk around the shop, focused on an SRT-8 in progress. "They know how to make an engine work.''

Start with the basics: Bore it out by three millimeters to up displacement from 5.7 to 6.1 liters (6.059 actually), bump the compression ratio to 10.3:1 from the standard 9.6:1, install a high-performance camshaft. It goes deeper than driveway hot-rodding, though, and not only because Chrysler can make the electronics work in concert even while keeping it legal in the eyes of the feds. SRT improves the breathing with larger- diameter, hollow-stem valves and reshaped cylinder ports, fed by a new intake manifold (a thing of beauty under the hood that initially distracted us from the orange block) and steel-tube exhaust headers a quarter-inch larger in diameter than the exhaust manifold in the base Hemi. The SRT-8's block is reinforced and boasts increased coolant flow, the crankshaft is forged steel, the connecting rods are stronger powdered-metal forgings, the pistons run on floating pins and are cooled by oil squirters, the exhaust valves are sodium-filled, and the oil pan is modified for reduced foaming. With the stronger parts, the SRT version of the Hemi spins nearly 15 percent faster than the base model, putting redline at a respectable 6200 rpm (the electronic cutoff is at 6400) vs. the regular edition's 5400 rpm.

Torque rises to 420 lb-ft, so preservation of the five-speed A580 transmission requires a little more aggressive electronic "torque management'' in the way the engine and trans relate to one another. Keeping in mind the 300's base architecture is inherited from the parent company in Germany, Knott also had to draw on corporate knowledge by finding AMG's supplier of rear differentials and ordered up a part akin to that used on the mighty Mercedes-Benz E500 to couple to his beefed-up halfshafts.