DOes anybody use them i havent seen to many people use them. Alot of the LT1s i see have the stock pulley does the underdrive pulleys slow the car or do they help? Does anybody have any experience with the underdrives on the dyno ? any feedback would be great.

 

i heard the underdrive pulley also slows down the air pump, would this not make the car lose HP??? im not sure so im just wondering.

 

I have March 20% UD damper[not piggyback] pulley...
No probs with it the voltmeter goes by red at idle in gear but no real charging probs..
Many people don't use them, as the LT1 water pump doesn't drive off the belt it drives off a timing cover shaft... so there is less 'gain' than other cars..

bachehbad:
LT1 air pump is electric, not belt driven..
Also, it only runs a few minutes at start up...
And it certainly doesn't ADD HP [or take much away either!]
Maybe you're thinking an 'air pump' is a blower?
Charlie

 

i have one on my Z, have no charging problems what so ever, only time i notice a drop is when i turn on my manual fan switch.

here is a dyno chart:
http://www.ws6.com/mod-2.htm

next time try a search, you'd be surprised what you find....i think there are about a dozen posts for exactly what you asked.

 

I did do a search and i didnt find out what i wanted to know that is why i posted thanks for the input anyways