A gas-to-diesel conversion boosts a Hummer's mileage from about 10 miles a gallon to between 22 and 24 miles a gallon. Additionally, the horsepower jumps from about 325 in the regular Hummer to 650, giving the car more power.
Goodwin, who's based in Wichita, Kan., doesn't advertise or push the services through Web sites much because it generates too many inquiries. "I really get pounded with a lot of requests when I do," he said. "But it doesn't look like I will be able to hide much longer."
Gas-to-diesel conversions are the automotive equivalent of a heart transplant. The gas-burning engine and original transmission are removed and replaced with a Duramax diesel engine, typically inserted in Chevy trucks, and an Allison transmission.
With a Hummer, little retrofitting is required. With the Impala, the center divider in the car had to be widened. In the end, though, the car still accommodated four or more passengers, unlike the two-seater Lamborghini.
The performance increase comes in part from the inherent properties of diesel engines. Overall, a diesel can deliver more torque–the rotational force applied to an object, in this case the car's crankshaft–than a gas engine. A 500 horsepower gas engine might put out 600 foot-pounds of torque. A similar diesel might put out 800 to 900 foot-pounds of torque.
The engine inserted into the 1965 Impala cranks 850 horsepower and 1200 foot-pounds of torque. The Impala was chosen because it has a stronger frame than most other mid-1960s muscle cars.
