Underdrive Pulleys

sandman0023 · Oct 11, 2006

I have a set of Ford Racing Underdrive pulleys in my 89GT, 120 Powermaster alt & an Optima battery. I also just replaced the starter (for the second time in a year). My other mods are in my sig. The car sounds weak when I start it and while its running and the belt moves slow. I heard the problem is the pulleys and if I put the stock ones back on it will run better. Is this the only way to fix this issue?

Nopantz · Oct 11, 2006

what pulley do you have on the alternator......a fix might be to just put the stock pulley back on the alternator...most people will tell you that the alternator pulley will cause problems if changed and to stay away from it

PJB · Oct 11, 2006

But isnt a higher output alternator (like he has) supposed to correct the charging issue if using the underdrive pulley on the alternator?

Sicarius428 · Oct 11, 2006

Some alts. put out the amps at higher rmps. Correct me if I am wrong but the powermasters really don't start charging till 1500 rpm. Combined with UD pullies this can cause a problem. Webpage about powermasters and UD pullies.
http://www.powermastermotorsports.com/power_pulleys.html
I would start by just changing to the smallest alt pulley you have.
Kevin

Foxfan88 · Oct 11, 2006

i've heard alot of the higher amp alts have the same size pulley as an UD set would have. doesnt really matter though, i had charging issues with my UD pulleys so i changed back to stock alt pulley and its fine now.

gruvee87vertgt · Oct 12, 2006

I would check the tension in the tensioner and the belt.

srothfuss · Oct 12, 2006

Alternators only produce about 10% of their total output at idle. This is why your car "sounds weak"

The simple solution is to get an overdriven pulley for the alternator. This will spin the alternator up faster and sooner so your electrical system isn't relying on the battery as much.

gruvee87vertgt · Oct 12, 2006

srothfuss said:
Alternators only produce about 10% of their total output at idle. This is why your car "sounds weak"

The simple solution is to get an overdriven pulley for the alternator. This will spin the alternator up faster and sooner so your electrical system isn't relying on the battery as much.

so does that mean he needs to put the stock pully on?

srothfuss · Oct 12, 2006

it all depends on what pulley is currently on the Crank / Water Pump and alternator. In my case I ran the BBK steel underdriven pulley kit. It came with a smaller crank pulley, water pump pulley and Alternator pulley. When I put them on, i instantly noticed a huge drop in voltage. Even with a 3G alternator I still didn't have the voltage I wanted (with the U/D pulley kit on) until I switched to the overdriven alternator pulley.

You also had a very good point about the tensioner. When I swapped out my pulley set, I my belt tension was out of spec and I needed a shorter belt to correct it.

sandman0023 · Oct 12, 2006

I have the correct belt. I'll attempt to find a stock alt pulley then. I sold mine on Ebay after I installed the underdrive pulleys. Thanks.

Flavadave4 · Oct 12, 2006

I will never run an underdrive alt pulley, stick with the stock one!

whtpny · Oct 12, 2006

I have a stock alt. here if you pay the postage I will get the pulley to you.

Maryland Stang · Oct 13, 2006

The underdrive pullies sure do catch a lot of grief here. I ran mine for 4 years with underdrives. Sure, it would only show about 11 volts at idle but fortunately for me I rarely drive around at an idle. 4 years with a Sears Diehard battery and never once did I have to get a jump start or have to charge the battery.

stangjunkie · Oct 13, 2006

sandman0023 said:
I have the correct belt. I'll attempt to find a stock alt pulley then. I sold mine on Ebay after I installed the underdrive pulleys. Thanks.

the guy you sold it to.... he had to buy it cuz he did the same thing

Underdrive Pulleys

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