Ok, I've been doing a little research on the pros and cons of installing the underdrive pulley for a little extra hp, and am generally sold on installing one because it seems to give you the most hp bang for the buck. One comment I came across that alarmed me, however, was the following comment in this article: "third, the pulley also is without the ‘harmonic balancer/torsional damper’ meaning if the crank isn’t within certain tolerances (tight factory spec.) it could cause a ‘wobble’ in the crank, leading to premature bearing wear."
Full article here (yes, I know they're referring to Z cars, but I figure it applies universally):
http://www.nicoclub.com/archives/300zx-z32-underdrive-pulley.html
So I guess my question is, if installing an underdrive pulley means upsetting the balance of the crank/engine, is there any aftermarket UD pulley out there that addresses this concern? I would like to get an extra 5-8hp and am willing to sacrifice some a/c cooling efficiency, but not at the expense of engine longevity if it means premature engine wear.