Unorthodox Racing aluminum crank pulleys on average can provide gains of 5 to 14 HP and 4 to 12 lbs.-ft. on normally aspirated engines and 8 to 18 HP and 8 to 14 lbs.-ft. on forced induction engines. Higher gains are possible. For example, a Nissan 300ZX twin-turbo saw gains as high as 37 HP and 45 lbs-ft. on the dyno just by replacing the stock crank pulley with our Ultra S series lightened underdrive crank pulley.