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There' s nothing better than the sound of a big-bore V8 in the morning. That is unless you can lower the car' s top at the touch of a button and enjoy it all the more, like we did in the 2007 Mercedes-Benz CLK63 AMG. The new 6.2-liter engine, designed from scratch by the powerhouse AMG division of Mercedes-Benz, features a wildly "oversquare" design; that is, the diameter of the cylinder bores (102.2mm) is larger than the stroke (94.6mm) of the pistons. In other words, you can almost distinguish each discrete explosion as the high-compression (11.3:1) engine bellows through the free-flow dual-tipped exhaust. For gearheads, it' s one of those uniquely identifiable exhaust signatures that can only come from an engine of that design.The new V8 is, or will be, at the heart of several 2007 AMG-equipped offerings, and in this application, it produces 475 horsepower at 6, 800 rpm, and 465 pound-feet of torque at 5, 000 rpm. That represents a 30-percent and 24-percent increase over the 2006 CLK55' s 5.4-liter output.Surrounding the magnificent new engine is an updated version of the CLK Cabriolet, suitably wearing new badges and bodywork, and new 18-inch wheels surrounding fade-resistant composite-construction front brakes discs. Once again, it appears that the U.S. market will not enjoy a coupe version of the CLK in AMG dress, although we drove one of those as well.Big power, big smile Our drive route comprised a healthy mix of freeway, sweeping rural highways and farm roads that showed off the engine' s particularly wide-ranging abilities. Most of the time, the engine loafs around town, shifting at say, 2, 000 rpm, using just about an inch or two of the throttle pedal. But that doesn' t mean the car is slacking. On the contrary, even at moderate engine speeds below 4, 000 rpm, the 6.2-liter V8 is more than capable of propelling the 4, 100-pound car with authority. Indeed, the torque plateau begins at just over 4, 000 rpm and tops at 5, 000.Only when the road straightens out can a driver use all the throttle. When he does, the world goes all streaky and blurry ' round the edges as the tachometer slowly sweeps toward its rev limit just over 7, 000 rpm. Speed seems to build exponentially because there are so few shifts occurring, and each gear feels like it lasts twice as long as one would expect from a seven-speed transmission. Most of that' s due to the rather tall (2.65:1) final-drive ratio in the rear end, but the effect is one of limitless acceleration. Mercedes claims a 4.7-second 0-62-mph (100 km/h) time (in 2nd gear), and the shift from 3rd to 4th doesn' t occur until you' ve surpassed 100 mph. That' s some tall gearing.The car is electronically limited to a top speed of 155 mph, but doing the math reveals a real potential for just over 200 mph in 5th gear, assuming it could push that wall of air. The other byproduct is that fantastic soundtrack issuing from the tailpipes. When the conditions are right, you can actually hear spent gases rushing through the system like the great big air pump that it is.
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