This power pulley will definitely boost your SC up! This combination of power pulley with a slightly smaller belt, will increase your horsepower and torque.This is specially designed for the Thunderbird Supercoupe and eliminates any slippage that may occur. This pulley is neither a 5% or 10%....somewhere in between. This pulley and belt kit will increase boost to 10-15lbs., it will pick up 25-30 horsepower and 40-45 ft.lbs.of torque as per manufacturer.