Bones Z28

iTrader: (8)

I was just wondering if it's worth getting pullies for an LT1. I know a lot of mustang guys do it, even seen a LS1 with a set on. Supposedly the smaller pullies will add a few horsepower, but what do you guys think. I'm worried that it will drain the battery, because if the pullies are smaller it's not working so hard (the hp gain), yet that means the alternator isn't working so hard right? That's why I'm worried that my battery might not probably charge. Idk someone help me out here lol.

blue94

iTrader: (7)

most kits have an oversized alternator pulley to make up for the slower belt speed because of the underdrive crank pulley. Unless you are running out of other bolt ons to do, I would spend the money elsewhere. Since our waterpump is driven by the cam gear, the pullies don't make near as much difference as they would on say a mustang.

Mighty Whitey

REAL WORLD GAIN:

FACT:my '95 formula does NOT have underdrive pullies
FACT:my friend's '97 trans-am DOES (crank and alternator)

FACT:I took the belt off my car, and picked up 10rwhp on the dyno
FACT:he took the belt of his car, and picked up 4rwhp on the dyno

FACT:same dyno, same day, back to back runs for both cars.

OPINION: seems to me that there would be a 6hp increase by putting a set of underdrive pullies on my car.

I don't know how much more proof you would need, but there it is. they obviously work, IMO

koolaid_kid

iTrader: (21)

I put a set on my car, which was basically stock at the time. I did not dyno it, but the seat of the pants test told me that I had gained hp. But you must put the alternator pulley on as well. I did not at first, and killed the battery sitting in line at the track. I now have the alternator pulley on the car.
One note: your steering will get firmer at low speeds, such as in parking lots.
There are probably other things that will get you more power for the money, but they do work, in my experience.

thesoundandthefury

iTrader: (3)

This is the one you need:

http://www.lmperformance.com/3668/2.html

The crank pulley is an underdrive balancer that totally replaces your stock balancer. This is better than the kits that just use a solid billet pulley for the crank that you have to "piggyback" to your stock balancer, which just add dead weight to the rotating assembly.

Formula350

iTrader: (3)

Not a bad price, since the March kit is $110, in Summit that is.

EDIT: Re-looking at those on LMP, why does it say 23%/15% and then 34%/15%??

thesoundandthefury

iTrader: (3)

It's a typo. ASP also makes a 34% underdrive crank pulley too, so it looks like they got the description confused.

Timbo

We use a 25% underdriven pulley alot here in australia. I havent heard of people changing the alternator pulley either, everything seems to run fine afterward. Its a pretty popular mod here, doesnt make huge gains but does make a difference.

koolaid_kid

iTrader: (21)

Make sure it comes with the belt too.

dhdenney

iTrader: (53)

I couldn't tell much difference when I had one, but mine was a piggyback too. That ASP pulley might do the monkey, IDK. So let's say it does pickup some horses, I call on the 2-3 mpg claim.

ecniv

iTrader: (1)

I had one, didn't run a larger alternator pulley... The charging system couldn't keep up with the electric water pump and the fans if I had both on. The car ran very poorly, and my Scanmaster was only showing about 11 volts. I removed it, and everything was fine. I gave it away to the first person with an LT1 that I saw.

imnotplutonium

iTrader: (4)

I am thinking of taking mine off as well. I have had charging problems ever since I got the set. It is not bad enough to kill my battery but at a stop light or just idle I will only put out like 11 volts. And this is with the alternator pulley. I did this mod with new spark plug wires, cat-back, and 3k stall with rebuilt tranny. I saw the same number I had made on the dyno before all of this was put on. I think maybe 1 hp more. the torque was higher though.

But here is the catch. I am actually not sure if it is the pullies fault. When my car is off, the battery slowly drains down to like 11 or 10.5 volts. My alarm stopped working because of this. Maybe just a short somewhere causing all the problems?

James Montigny

iTrader: (13)

Pullies on an auto with EWP probably not a good idea unless you install the alt pully as well.

LT1Formula007

iTrader: (66)

I have the underdrive crank pulley on right now and it has killed my battery 3 times now. So now I have to rev it up a little bit at lights to get it to charge right. So I finally bought a OD Alternator pulley last week, but haven't gotten around to putting it on yet. Wish me luck.... oh as far as HP, I could feel a difference as well.

thesoundandthefury

iTrader: (3)

To really do a set of underdrive pullies "right," you should do them along with a tune that will bump the idle up slightly. (50-100rpms.) The guys who're having charging problems are usually running the bigger 34% underdrive pullies with no overdrive alt pulley at the stock idle RPM. There's no free lunch.

Formula350

iTrader: (3)

So for me, with my idle @ 550, it wouldn't be a good idea?

I really don't want to have to get another chip re-burned if I was to go that route :\

LT1Formula007

iTrader: (66)

Thesoundandthefury is absolutely right about the stock rpm and the bigger 34% UD Pulley with no OD Alt. pulley. I had to find out the hard way, now like I said you could always rev your car up a little bit but dang it that gets annoying. If your gonna do it, just do it all the right way the first time you do it. IMO

imnotplutonium

iTrader: (4)

yea I have found this to be true. I do have the overdrive pully but my idle rpm is low like 550. I think I'll bump it up to 700 when I get home if I have time and let you guys know how it goes.

borninatransam

iTrader: (4)

save the money. buy an electric water pump. look at the big dogs on here and tell me how many run underdrive pulleys.

James Montigny

iTrader: (13)

To be fair, most of the "big dogs" don't run power steering or a/c.
In some cases, they run a short belt or no belt at all.

Since LT1 water pumps are cam-driven, power gained from UD pullies really
has nothing to do with water pump (mechanical or otherwise).