stillen pulleys
 

On the stillen website it have a standard crank pulley and a underdrive crank pulley what is the difference between them and how hard are pulleys to put onto my 370z roadster

The standard or stock size pulley is a light weight pulley. All the accesories will spin at the factory speeds but because of the weight factor the engine will rev a little faster. The under drive pulley is light weight also but because it is smaller all the accesories will spin slower(alt. a/c etc.), this will result in a faster rev up and a little more horsepower. Not super difficult to install, but care must be taken to get the new pulley lined up true. If you haven't done one before, I would suggest having someone who has, help, or paying someone to do it.

i started the exact same thread with almost the same OP about two weeks ago haha

Sorry to bring this back from the dead but I am a bit confused. The stillen Crank Pully replaces the main crank pully. So does the UR one? I have both of them in a box waiting install. Am I using one or the other?

they are both replacements for the crank pulley, you use either one or the other.

So I'm guessing he bought 1 and then the other later on, when he went supercharger he didnt need either. I'll use the standard Stillen Crank Pully not sure about doing the under drive pullie. So... I have a Under Drive pullie from Stillen for sale.