Do I need to put the supplied pulley to the old balancer ,wont the belt be pulled at an angle then?

 

Take the old one off put the new one one you will be fine

 

In the directions it says the bbk one goes ontop of the stock one

 

Anyone do these?

 

i wouldnt use these on most engines. most of the crank pullies today are balanced with harmonic balancers to help keep vibrations down and wobble.

also when you underdrive the engine accessories they get less drive % then ford wanted from factory. so your alt will turn slower, power steering, and anything else connected to the serptine belt.

if your looking for power consider full exhaust, intake and a tune for mild gain 10hp-20 or forced induction for best results. the underdrive will add power but its at a cost and the cost is to spin your necessary componets at a slower rpm. something the ford engineers didnt design it for.

but it could be good fo you never know. for me it isnt

 

I just returned a set of BBK underdrive pulleys to Summit because the piggyback crank pulley was standard thread and my balancer is metric. But yes, the crank pulley bolts to the back of the original balancer/crank pulley. The original is a balancer and the new OD pulley is just a pulley, you still need the balancer/damper on there. Test fitting also showed me that it put the balancer dangerously close to the fan - not a risk I wanted to take.

As for whether it's a good idea, I'm still a believer in them as long as you understand the trade offs involved. All the accessories that are belt driven are set with their factory ratio to give you full results at/near idle. With OD pulleys you don't get that, you will typically not get a charge from the alternator (or at least not much of one) unless the rpm's come up. But then, at factory ratios the alt hits full charge around 1000-1200 rpm. With OD pulleys you're probably looking closer to 1800-2000 rpm for full charge. Not good if you sit in stop and go traffic, idle a lot, and crank up the big stereo. Fine if you are usually in motion and don't have super overdrive with 2.73 gears.

The OD will slow down the other stuff too (although usually not the water pump, that's why the BBK's come with a larger water pump pulley), so you may not get full power steering out of the deal. Not sure, since I didn't actually put mine on the truck. I've had them on my Mustang 5.0 for about the last 80k or so and haven't noticed any issues, although I've seen magazines bashing OD pulleys lately...