The Turbo I engine was modified with pre-production pieces from what would become the Turbo II inline-four engine. These changes included an intercooler, plus other changes to produce 175 hp (130 kW) and a flat 175 ft·lbf (237 N·m) torque curve. Not included were any of the durability changes to the short block (forged crank, full floating pin, stouter connecting rods, etc.) of the 1987 Chrysler Turbo II engine. Luckily, the Shelby engines have proved to be reliable even without the durability enhancements of the production Turbo II. Performance was impressive, with just 6.5 s needed for 0–60 mph (97 km/h) and 14.8 s for the quarter mile (402 m) run. Top speed was 135  mph (217 km/h).