Okay, neophite question here. Seems like everyone knows what it is, but I'm clueless! Can someone tell me the details regarding an "underdrive pulley"? How does it improve performance? . . . Or does it? I assume it's either a larger or smaller belt pulley (smaller seems logical - assuming it's the crank pulley, slight mechanical advantage???). Which pulley is it? How do I tell if I already have one?

My car is a Specter Werkes car -- 1998 Vert, built by Specter Werkes when it was brand new, then sold new by dealer. I know the motor was built by Katech. It's a 382 Stroker (yep, not a 383), forged crank and pistons, 11:1, billet rods, comp cam (224/228, .585 lift, 113 degree lobe separation), stock Z06 heads, stock injectors, stock throttle body, TPIS long tubes, stock cats & exhaust, Halltech A/F. Dyno'd at A&A @ about 412rwhp/450rwt if I recall correctly. A couple of guys told me that A&A's dyno (not his new one) seems to read about 4% under other Dynojets (not that it matters). So if I don't already have an underdrive pulley, what would I excpect to gain? Does it require a different belt?

Thanks in advance!

Oh, and BTW - Any suggestions as to the next logical step to eek out a bit more HP invited as well. Thanks!

 

An underdrive pulley replaces the stock crank pulley, and causes the accessories to spin slower. It has been dyno'd to add about 10 hp, but is a beetch to install as you have to move the steering rack to get to it. Most do it in conjunction with heads/cam, not alone.

 

Thanks!