Tony71502

You probably could if they were custom or somthing of that sort. I believe theres another belt added when supercharging? I dont know im a N/A kind of guy. Which would require a crank pulley with 2 belt tracks. But even if there isnt another belt added, im pretty sure that the supercharger is designed for stock belt systems, and running it with an underdriven system would cause the supercharged to be underdriven as well. In which case alargerS/C pulley is needed to compensate... Just like some do with alternators.

96FLMustang

Are the U/D pulleys worth it? How much power could I expect to gain at the wheels on a 94 GT?

Tony71502

My fox was 99% stock except the fan,but I could definatly notice it. It made my car run quieter since the flex fan is noisy and now it doesnt spin as fast. My stock pulleys were also caked with dirt. I ditched my A/c at the same time. Basically it didn't break em loose in first gear before... now it does. (that's with the clutch fully engaged, none of that dumping that ricers need to do to break em loose.)

96FLMustang

Thats good to know. I'm hoping it can take off .3 at the track. I think I'm gonna get some pulleys now.

67mustang302

u/d pullies will prolly make you run down to around 12v at idle if you have accessories running. In my 67 I go to about 12v if only the brake lights are running when it gets down to about 700rpm, with headlights/heater going in the winter it gets down to 12v at about 850-900rpm. That's with a 140a alt. Anything after that it runs at a consistant 14.5-14.8 volts. Any charging problems when the car is moving are not a result of u/d pullies, but a bad electrical/charging system. And if you get good power pullies you should feel a difference

AndySpeed

ya last summer i had to have a custom built alternator for mine.. theres a spec sticker on the side ill get the specs next time im in the garage.. mines aways around 13volts..