Throttle Body & Pulley Swap: Finding Those Last Few Horses

05. After installing the pulleys for the first time, we realized that the stock drive belt would no longer be the length needed to fit around all of the engine accessory pulleys. We figured out what length was needed, and wrote down that length with a paint pen behind the grill of the Bronco so it would always be easy to reference.

06. Here’s the throttle body box and all of its contents. The BBK Power-Plus Twin 56mm throttle body is CNC-machined from 356 aluminum castings to ensure a perfect OEM-quality fit. OEM die-stamped throttle linkages, double sealed bearings, O-ringed throttle shafts, and a rugged frame combine to make this a somewhat sophisticated and robust part. This throttle body is designed to get the vehicle’s engine every bit of air that it can utilize in order to run as efficiently as possible. More usable air to the engine will mean more power.

07. The installation of BBK’s 56mm throttle body was pretty simple—it primarily involved removing the hose clamps from the stock unit, unbolting it, and replacing with the new stuff. One piece of info that can be helpful: in many vehicles, the fuel lines will remain pressurized even when the engine is not running, so if you decide to undertake a throttle body swap, be careful not to end up spraying your face with gasoline. This just may have happened to us at some point in the past…we’re not telling.

08. Here’s the old stocker throttle body we pulled off the Bronco. Eighteen years of use had taken its toll—check the corrosion on the inlet and outlet tubes on either side of the unit. BBK makes performance-oriented throttle bodies and underdrive pulley kits for most late-model vehicles (including a larger 61mm unit that would have also fit our Bronco). Check out their website (listed below) for a complete list of applications.

09. We had the Bronco in the sand just a few days after the underdrive pulley kit and throttle body were installed. Many times, when we install smaller-scale performance mods like these, it’s difficult to feel a power difference from the driver’s seat. In this case, we could actually feel some increased pep. And we’re happy to report that we didn’t detect a noticeable loss of efficiency from the A/C system, the alternator, or any of the other accessories driven by the engine pulleys and belt. It looks like we can chalk this up as a win/win.