i was flipping through a parts catalog and came across a set of underdrive pulleys for 289/302's with v-belts. i put underdrives on my 94 lightning and saw a big gain but are they worth it for v-belts?
I've run my 331 powered Comet with both and there's no difference. I went back to a slightly overdriven waterpump pulley just to help insure the car doesn't overheat. Underdrives are possibly a good idea in "Ricers" that are extremely limited in power and torque, but on a 300+ hp V8, they're a waste.
I put the under drives on my 289. It was the only way to stop the 3G alternator from squealing. The v-belt doesn't have enough contact area to pull the 130 amp load.