if i were to have underdrive pulleys on my car and i got a supercharger can i leave the underdrive pulleys on or would i have to put my stock ones back on

 

stock

 

why though i dont understand

 

It depends on the supercharger igot a kb and they gave me an underdrive pulley for the crank, you can leave it on but then you will just have to run a smaller supercharger pulley but its better to run bigger pulleys for more belt wrap and less chance of the belt slipping. The sp and crank pulley is waht determines your boost.

 

sc and crank*

 

hmm following

 

As you know, underdrive pulley kits work two ways. First they are often lighter than stock. Second, they are smaller in diameter and actually turn the accessories less. Your crank turns less per RPM of the engine, and the same thing with the water pump, alternator, etc. That's why people often see alternator / charging problems with them.

Now look at how centrifugal superchargers work. They work via a belt is thrned by the crank. So if you have a smaller crank pulley that is turning fewer RPM, then that means that your supercharger pulley is going to be turning less RPM (just like the water pump and the alternator.) And if your supercharger is turning less RPM, then it is producing less PSI.

Make sense?

 

thats only if the sc is running on the same belt that the accessories are which for most fox body sc, thats not the case. only the KB uses the accessory belt to run the sc. the problem with a vortech or paxton while trying to run UD pullies is that they provide a crank pulley with the kit that would replace your UD.......of if you get a base kit, they give you a sc crank pulley that bolts inside the stock crank pulley and most UD pullies are too small for the sc crank to fit inside. and lastly, a sc adds ~150hp.....UD add 5hp, dont you think its a smart idea to give up 5hp to get 150?

 

if its a vortech you just have to find a underdrive crank pully, with that you can run your underdrives. Try ebay to find one