what will a underdrive pulley kit do for my car? any performance gains?

 

a couple pony's maybe. buy used if you do it as spending full price on a set isn't worth it imo.

 

you'll pick up a couple of horsepower, but put yourself at more of a risk of overheating and killing the battery as the underdrive pullies slow down the speed of the front acessories.

I can vouch for the loss of altenator effectiveness at idle, my volt gauge is at the low end of the spectrum when the lights and heater are on but my car has NEVER overheated...

my car also had them on when I bought it, personally I wouldnt spend the money...

 

ya mine had them when i bought it too.. def notice the voltage drop at night at idle.. kinda blows. i wouldnt have bought them if they werent already there. for a DD i feel like the loss is greater than the gain. if you have any sort of good stereo in ur car i can notice the headlights dim when it hits. and you can watch the voltage meter bounce up and down. and heater on high with headlights on.. forget it this is all at idle btw

 

bump your idle up some? I myself and my buddy's '88 both have them and neither one of us have ever had problems at idle with charging or heating. l hear this all the time and wonder why the 2 cars I personally know never have the issues that i hear about.

 

Well you don't have a junk alt for a stock one either. Don't know about your buddy. The pulleys really don't cause much of an "issue" persay but like said before it does lower the charge at idle and the cooling efficiency but when you are driving around it isn't really an issue. Being a GT and using the foglights can also cause them to seem worse. But if you have a stereo system, electric fan, or any other items in the car that use much of any load can make the issue worse.

IMO I wouldn't spend the money on them. IF you do the aluminum would be the best decision prolly too because there will be less drag on the front of the motor allowing the engine to rev a little quicker.

 

I had them on my 87GT with stock alt everything does drop real low, and I never could let the car warm up on cold mornings because the car would sometimes stall from the cold start heater blowing and idling for 15 mins or so which sucked because once it dies out the battery is too weak to start it again. Even though I kept the stock alt pulley. I noticed a slight gain tho my car was stock otherwise. If every HP counts to you get it. Otherwise don't bother. My 2 cents

 

8 + yrs with the March Power and Amp UD pulleys and not one issue with either cooling or a charing and I still have the OE Alt, OE Radiator but I have no big stereo system either.

I'm a firm believer in that the UD pulleys weren't meant for high hp motors with cooling issues or huge stereo systems and if you have either then UD's are not the way to go.

And as far as Power gain there will be some but don't believe everything you read from any manufacture.

 

well i guess if i upgraded to the 3G alt that comes in the sn95s i would be fine

 

Same here. NEVER had it overheat, but it eats through batteries like candy. One a year.

"well i guess if i upgraded to the 3G alt that comes in the sn95s i would be fine"

That's what my alternator guy recommends for my car...