My brother has a 94 firebird v6 with underdrive pulleys for both crank and alternator and it has really low voltage at idle, so I figured I would just use an underdrive crank pulley without the underdrive alternator pulley on my 93 z28 and have it would have no charging problems.

But then I heard somewhere that if I use the underdrive crank pulley without the underdrive alternator pulley that it will mess up the charging of the battery.

Can someone tell me if I need the underdrive alternator pulley or not?

Thanks.

 

Generaly you wont see much gains on an lt1 anyways from underdrive pullys. So probly spend your money elsewhere.

 

Only one worth buying is ASP Pulley's. I just run one on the crank, and I have no problems with voltage. It's a 23% underdrive.

-Dustin-

 

I agree with the poster above, if you insist, I suggest using a higher amp alternator.

 

A large Amp alternator will place additional load on you engine and eat-up HP (not good for performance). It takes additional HP to generate those additional amps.

I'm underdriven on both the damper and alternator pulley (40% total), but still maintain a 13.5 float voltage at idle.

WD

 

As one poster saif UD pullies are worth little on an LT1 anyway so you would be better off to skip it BUT that said a stock car may experiance charging issues with just a UD crank pulley, with a cam requiring a raised idle though that issue should go away so look at people's mod lists when they reply to such threads.

IMO the only real benifit for UD pullies on an LT1 is to slow the accessories on a motor that sees a lot of high rpm use potentially extending the accessory life or delaying overheating of the PS system in road racing.

The AC and WP are the most parasitic accessories and the AC is shut off at WOT and when it shuts off based on throttle is reprogramable, the WP on the LT1 is not belt driven like it is on other motors. On motors with belt criven WPs underdriving van produce pretty good gains by slowing the WP and taking less power to turn it.

 

Even with the A/C shut-off, the A/C hub and pulley weigh about 3.5 pounds and it takes energy to spin-up all that mass to 6K.

Two extra HP here and another three there, then you just keep working on the small things and you gained another tenth.

WD

 

I had the ASP 23% U/D crank pulley, and 15% U/D alternator pulley, and on a hot day, sitting in traffic, the voltage would head for the red zone. And that's with the M6's higher idle rpm.

http://www.ws6.com/mod-2.htm

 

With the XFI-292 HR cam, my car idles at 1K. So, that is probably a factor with still maintaining 13.5 volt float voltage at idle.

WD