Underdrive advice

**emotionalpiracy** · 10-18-2007, 01:01 PM

my brain is melting from trying to figure out what underdrive pulley to buy. Can anyone provide a valid argument for their preference? So far all I have read is that alot of people prefer the SLP pulley because theres no chance of thrown belts and that its stronger than the ASP one. Yet other say that ASP never throws belts and the walls are unecessary. Then I began to find out that even though they all claim to be 25% underdrive that certain pulleys have different diameters. Then i started reading about elastomer pulleys, and then March fluid dampener pulleys. I am so lost.

**Hamrhead** · 10-18-2007, 01:43 PM

I have heard the SLP is better than the ASP. I used the ASP for 3 years and no issues. I now use an ATI and imo is the best one. Whichever one you get make sure it is SFI approved for at the track. You may not need it right away but it will leave you room to grow as your E.T.'s are lowered through modding. I would look into an ATI!

**rel3rd** · 10-18-2007, 02:32 PM

I bought a March fluid filled version from Summit for just under $200. It is SFI approved and it also has the higher edges on the pulleys to prevent belt tossing, even though I don't remember them advertising that fact. Mine also came with a brand new GM crank bolt. The new, smaller belts that you'll need can be bought at any parts store and I'd be happy to share the part numbers if need be.

**emotionalpiracy** · 10-24-2007, 09:53 AM

well i can get the SLP one on ebay for $193 including shipping which is generally rated at 10 hp increase, I can get the ASP for 190 including shipping which is about an 11 or 12hp gain without the alternator underdrive, or I can get the March for like 206 including shipping, which i have not seen any dyno numbers on. I was just wondering if it was worth it to go with March if it had better dampening ability, or if it is an insignificant difference in dampening ability?