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Throttle Body & Pulley Swap: Finding Those Last Few Horses

Ford Bronco Offroading
Dexter Roberts Jr. | Writer
Posted March 1, 2012
Photographers: Jason Sands, Kimson Ekman

A Throttle Body and Pulley Upgrade Squeeze Some Extra Power Out of Our EFI-Powered V-8…While Keeping it Smog-Legal

It must have been fun, back before emissions testing became the norm. Truck buyers were able to open their hoods and rip right into the engine, creating whatever kind of steroided-up Detroit-iron monster they wanted. Try that today and not only will emissions clearance be a problem, but the computer brain of the vehicle will likely throw a hissy-fit and disable the vehicle if not reprogrammed properly.

Thankfully, the aftermarket is always quick to come up with solutions for the modern power-obsessed vehicle owner. Companies like BBK Performance are constantly designing and testing parts designed to help engines reach their optimal potential. In some cases, this is accomplished by taking heat or strain away from the engine in order to limit the parasitic effect that load and temperature can create—things that tax the engine and rob it of power. In other cases, as most of us understand, power can be gained by simply helping the engine to accept all the air it can use. Recently, we got the chance to try both strategies when BBK sent us their Twin 56mm throttle body (to help the engine breathe) and Power-Plus underdrive pulley set for our project Bronco. Follow along for a full report.

02. Here is everything that is included in BBK’s Power-Plus underdrive pulley kit. The CNC-machined finish is quite attractive and should repel corrosion for some time to come. Less parts in a box can mean easier installations and less parts to lose—that was definitely the case here.

03. In fact, the only trouble we ran into at all was getting the stubborn nut off the alternator pulley as we started the installation. Be aware that these things are often difficult to remove! Here, two grown men try with all of their might to loosen the nut and end up looking like wimps.

04. Here are the installed pulleys after a weekend of use. These larger-than-stock pulleys dictate that the vehicle’s engine accessories will turn slower than they would than with stock pulleys. Additionally, they reduce the “moment of inertia,” which has to do with the power needed to cause motion and the distribution of mass being further away from the axis on which the pulley rotates. Simple translation: less parasitic power loss—the engine isn’t working as hard to drive the accessories. As you might imagine, aftermarket pulleys that aren’t designed correctly can cause the engine accessories to spin too slow, lessening their efficiency. That’s why it’s’ best to utilize a respected manufacturer like BBK.


BBK Performance
Temecula, CA 92590
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