Do these actually help our cars? I had the set (2 peices) on my truck and noticed a little but are they good for the lt1? Why do they sale them in single sets? Is it best to get the two?

 

I got a single integrated/one-piece ASP pulley for my '95. It noticeably pulls better in 2nd gear, and revs up more quickly. This version replaces the stock one, so you get less rotating weight on the front of the crank.

With my amps going, the V needle sometimes goes a bit below the 1/2-way mark. I imagine with the alternator underdrive pulley, it might touch the red area.

 

since the lt1 and ls1 engines have cam driven waterpumps, the advantage of the udp is not as noticable as on engines like the vortec trucks or the 3rd gen L98 or LB9.

however, spinning the accessories slower is still going to benefit to some degree. i had a march single crank pulley (piggyback style) installed on my 96z and noticed a bit more pull in top end and it seemed to rev up faster. granted this is mostly psychological, but i would say it was worth a solid 5-10hp, mostly in the upper rpm range. you wont really feel it around town. for about $75-100 i would say it was worth it.

and as for charging problems, i saw no drop at all. the only time i noticed a drop in voltage was when i turned my cooling fans on manually...which draws alot of power anyway...so that is expected.

i say look around for some used ones.

 

I'm with Teke. I got the March Pulleys. Dunno about no 5 to 10 hp because I didn't throw it on no dyno. I got it for free and just threw it on. I don't have any charging issues either. I heard that people who do have them are running good stereo systems and stuff.

 

Only LT1 has a timing gear driven water pump. LS1 is belt driven.

Keith at ws6.com dyno tested an U/D pulley, and got a peak power gain of 0.7 HP.... that would be 7/10's of one HP. Torque gain was about 5 ft-lb, and "average" HP gain across the full RPM band was 4.4 HP. Hard to believe that anyone could actually feel that small of a change. I know I had the ASP 23% U/D integrated damper/pullley and 15% U/D alternator pulley, and I could niether feel or measure any improvement. The charging system wasn't too happy with that combo in hot weather, or with the headlights and brake lights on.

 

The two piece set is designed to keep your alternator turning at the same speed (so you don't loose any charging/power capability) while reducing the speed that you're turning your power steering/AC, etc. I ran a pair for a while and didn't notice any change in performance.