Unorthodox Racing pulley sets on average can provide gains of 8 to 15 HP and 6 to 10 lbs.-ft. on normally aspirated engines and 10 to 18 HP and 10 to 20 lbs.-ft. on forced in duc tion engines. Higher gains can be realized on vehicles that are modified. These gains are obtained in two ways. First, and most important, is the weight loss. There is an average of 2.7 HP gained from every pound lost off the crank shaft. With the lighter accessory pulleys, as much as 15% to 30% more power can be found. 85% of our gains are from weight loss. The rest of the gains are from underdriving, which accounts for about 15% of the total gains. Unorthodox Racing does not push underdriving more than 20% for two important reasons. The main reason is to keep charging systems, air conditioning, ower steering, and water pumps moving fast enough for every day driving. Second, not much horsepower is gained from extreme underdriving.

All underdriving is done with the crank pulley, not the accessory pulleys (most applications). This is done so maximum weight loss can be achieved at the crank where most of the horsepower gains are found. The accessory pulleys for most applications are stock diameter. Since the Ultra Accessory pulleys are the same diameter as the stock units, you may install an Ultra Street crank pulley as a first step. Then, at a later date, you may purchase the accessories and install them without having to change belts again (on most models).For certain applications underdriving ratios are modified with the accessory pulleys when underdriving is not feasible with the crank pulley.