Looking at underdrive pullys for my d16z6. I read that they need to be balanced? Is this absolutely necessary? I know the most important thing is that it's lighter than OEM to take weight off the crank. But I mean there's pullys on ebay for like $20, are they worth it? Here's a link to one:
http://cgi.ebay.com/ebaymotors...&rd=1

 

think of you wheels and what happens when unbalanced. if they arent balanced then it will cause a wobble and good chance of timing belt coming off or breaking.

 

Don't do it, unless you get the AEM ones. Honda uses a harmonic balancer in the pully to keep vibration and shock loading from destroying your motor. The cheap ones don't have that. And if you're running stock, they won't make a bit of difference as far as noticeable performance.