The Ford Shelby Cobra GT500 show car provides a powerful choice in an efficient and clean package, especially considering muscle cars of the past.

"When you consider pony cars of the 1960s, today's engines produce approximately double the power, four times the fuel economy and 100 times fewer emissions," says Tom Jones, Ford SVT program engineer.

Performance cars have evolved dramatically since their heyday in the 1960s. In terms of safety, efficiency and refinement, today's street machines totally outperform their elder muscle car colleagues in nearly all categories. Yet the story is seldom told about the tremendous gains made in reducing emissions while increasing overall power output.

The fact is the GT500 is easily twice as powerful as the hottest V-8 package offered when Mustang was first introduced – yet still produces from 100 to 300 times fewer emissions. Additionally, today's modern "MOD" V-8 powertrain enjoys a nearly 60-percent increase in average fuel economy compared to corresponding Ford products produced 30 years ago.

Back in the so-called Muscle Car era, driving a street beast with more than 400 horsepower was a dicey proposition. When dual carburetors, progressive linkage and dual-point ignitions were part of the equation, performance came with a price – drivability. Running too lean or too rich – or with the timing or spark out of adjustment could mean it would misfire or "carbon up" – sometimes with thick, black smoke coming from the tailpipe. Worse yet was fuel economy, with most of the big, high-powered V-8s at the time netting anywhere from six to 10 miles per gallon (mpg) in typical driving.

Modern, race-derived technology provides an interesting power comparison: The GT500 with a 5.4-liter, DOHC, supercharged V-8 produces nearly 100 horsepower more with nearly 100 fewer cubic inches versus the 1967 Shelby GT500's 355-horsepower, 428-cubic-inch-displacement, big-block V-8.

Creating a powerful engine means designing it to be as efficient as possible, making the most of the fuel and air that makes it run. The benefits are not only seen in overall power, but in reduced emissions and improved fuel economy as well.

For example, the GT500 uses four-valve, double-overhead-cam cylinder heads for optimum engine "breathing." Using multiple valves per cylinder provides the engine with a more efficient airflow, generating higher peak horsepower. As an additional benefit, multi-valve engines better utilize the air-and-fuel mixture in the cylinders with less waste and unburned fuel vapor. Also, multi-valve engines are better suited to help scavenge exhaust gases out of the cylinder after combustion is complete for more power with cleaner tailpipe emissions.

In addition, supercharging produces the peak horsepower of a much larger-displacement, naturally aspirated engine. Yet, at lower throttle applications, the smaller displacement enabled by supercharging consumes less fuel, resulting in increased fuel economy and lower emissions.