[Formulajones]

Most all of the GM solid lifter cars had underdrive deep groove alternator pulleys to go along with the rest of the deep groove pulleys. Doesn't spin the alternator as fast as the typical conventional pulley.

My Z still has it's original setup on the factory 37 amp alternator.

I had another one of those alternator pulleys I ran on the Chevelle for years. Same 37 amp alternator. Doubt it does a darn thing for HP but it sure helps keep the belt on when you zing it.

I later switched to a 55 amp alternator, same pulley. I later switched back to the stock tiny steel pulley to up the juice during idle conditions.

Maybe I lost a 1/2hp