Underdrive Pulley Thoughts?

Tincan18 · 08-26-2004, 03:07 AM

I have a 1994 Mustang Gt and i was thinking of getting a BBK underdrive pulley Kit for my car and was wondering if it would make a noticable difference in my cars performance?

Mustang_289 · 08-26-2004, 06:17 AM

You won't see or feel any noticeable difference IMO. If you add up several of these small cheap mods, where the total = 20+ HP gain, you will see and feel a change.

You will notice if you've got a stock alt, that your lights will dim when your stang is sitting and idling at night. We upgraded our alt to a 3G 140A unit, no problem now.

crazypete · 08-26-2004, 09:17 AM

Isnt underdriving a larger alternator basically cancelling out the underdrive pulley's purpose? Just wondering cause I could use some extra juice to run all this stereo equiptment but my UD pulleys keep the ammeter needle dangeously low at night with the lights on and my stereo going.

GhOsT6_9 · 08-26-2004, 11:27 AM

Well on my car my best before the pulleys was 13.62@99, put on the pulleys an went a best of 13.33@101.

No charging or cooling problems.

88fivepointoh · 08-26-2004, 03:44 PM

i agree that some people like them and some don't bother.. I wouldn't bother, on a stcok car not with it and you will have the charging problem at your door.. The upgraded alternator is best, but for the cost your going to spend its not worth it. A cold air intake or TB upgrade would be better or headers.. Headers are #1 upgrade for power.

GhettoPop · 08-26-2004, 10:39 PM

i got a set of march underdrives. not a huge gain, but i did feel a LITTLE something. i also have a pa performance alt. although the stock voltage gauge drops a decent amount with lights on and sitting on the brake pedal, no charging issues. the UD's work by providing the alt with a smaller pulley, thus turning it less and robbing the the engine of less power. the pulley that came with the pa performance alt was smaller than stock, and the march UD pulley was even smaller. march also makes a "power and amp" kit which comes with a larger alt pulley. if your really concerned about charging and dont want to spend the dough on an alt, buy the UD kit but use the stock alt pulley and your should be fine. if a UD kit gives u 10 rear HP, leaving on the stock alt pulley will give u 9. u can even buy a bigger pulley for more charging

Mad Horse · 08-26-2004, 11:32 PM

I also have the March underdrive pulleys and did notice a difference after I put them in. Its not huge by any means but was worth the money. As far as charging goes.....that all depends on how big a stereo you have or the amount of accessories you are running. Some people keep their stock pulley on the alternator to help out with charging.

08-26-2004, 09:17 AM	#3
crazypete Registered Member Join Date: Sep 2002 Location: Boston Posts: 592	Isnt underdriving a larger alternator basically cancelling out the underdrive pulley's purpose? Just wondering cause I could use some extra juice to run all this stereo equiptment but my UD pulleys keep the ammeter needle dangeously low at night with the lights on and my stereo going. __________________ 91 GT Carb conversion, holley 600 double pumper, edelbrock performer intake, FMS "C" drop springs, march 1000 underdrive pullies, crane 1.7 roller rockers, GT-40P headers, bassani x pipe, american thunder catback, FMS 4.56's, msd aL6, trunkmount battery, A/C eliminator kit, 3000 stall tci streetfighter, AOD with transgo kit, A+ servo, 300M hardened lockup shaft, kevlar bands and 28,000 gvw trans cooler, 3 core radiator, 300 lbs stripped with a full interior

08-26-2004, 11:27 AM	#4
GhOsT6_9 Registered Member Join Date: May 2000 Location: Ontario,Canada Posts: 233	Well on my car my best before the pulleys was 13.62@99, put on the pulleys an went a best of 13.33@101. No charging or cooling problems. __________________ 1989 Mustang LX Notch 5.0L, T-5, 1969 351W heads, cut & welded stock plenum, F-303 cam, Mac 1 5/8 full length headers, Cat'd H-pipe, 3.73 gears, Underdrives, SSM lift bars, E-Fan, 3G Alt, Custom Chip, Autometer gauges, Weld Draglite wheels , M/T ET Street Radials Best 1/4: 13.33@101.53MPH

08-26-2004, 10:39 PM	#6
GhettoPop Gimme a Drink! Join Date: Dec 2002 Location: NYC Posts: 694	i got a set of march underdrives. not a huge gain, but i did feel a LITTLE something. i also have a pa performance alt. although the stock voltage gauge drops a decent amount with lights on and sitting on the brake pedal, no charging issues. the UD's work by providing the alt with a smaller pulley, thus turning it less and robbing the the engine of less power. the pulley that came with the pa performance alt was smaller than stock, and the march UD pulley was even smaller. march also makes a "power and amp" kit which comes with a larger alt pulley. if your really concerned about charging and dont want to spend the dough on an alt, buy the UD kit but use the stock alt pulley and your should be fine. if a UD kit gives u 10 rear HP, leaving on the stock alt pulley will give u 9. u can even buy a bigger pulley for more charging __________________ 1990 GT,stock T-5,K&N w/o air silencer,March underdrives,FMS wires,timing@14*,PA Perf 130amp alt,Steeda Tri-Ax Shifter,Steeda adj quadrant/clutch cable/firewall adj,Centerforce II clutch,o/r x-pipe,Magnaflow SS catback,g-load brace, subframes,Bilstein struts/shocks,Autometer gauges, 136k and running strong!

08-26-2004, 11:32 PM	#7
Mad Horse Registered Member Join Date: Sep 1998 Location: Dayton, OH., United States Posts: 467	I also have the March underdrive pulleys and did notice a difference after I put them in. Its not huge by any means but was worth the money. As far as charging goes.....that all depends on how big a stereo you have or the amount of accessories you are running. Some people keep their stock pulley on the alternator to help out with charging. __________________ 88GT Performance Mods: 3.73 gears, T-5Z trans, King Cobra clutch, Pro 5.0, Alum. DS, WMS Xtrac subframes, DynoMax Cat-back, PS91 Coil, March alum. Pullies, Fluidyne Rad, Elec fan Cosmetic Mods: Color change interior & exterior, Cervinis Ram air hood, 16" Ponies, LX Taillights. "Nip it in the Bud"

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08-26-2004, 03:07 AM	#1
Tincan18 Registered Member Join Date: Sep 2003 Posts: 16	Underdrive Pulley Thoughts? I have a 1994 Mustang Gt and i was thinking of getting a BBK underdrive pulley Kit for my car and was wondering if it would make a noticable difference in my cars performance? __________________ Tincan18

08-26-2004, 06:17 AM	#2
Mustang_289 Registered Member Join Date: Sep 2001 Posts: 512	You won't see or feel any noticeable difference IMO. If you add up several of these small cheap mods, where the total = 20+ HP gain, you will see and feel a change. You will notice if you've got a stock alt, that your lights will dim when your stang is sitting and idling at night. We upgraded our alt to a 3G 140A unit, no problem now.

08-26-2004, 03:44 PM	#5
88fivepointoh Registered Member Join Date: Aug 2002 Location: Rochester Posts: 553	i agree that some people like them and some don't bother.. I wouldn't bother, on a stcok car not with it and you will have the charging problem at your door.. The upgraded alternator is best, but for the cost your going to spend its not worth it. A cold air intake or TB upgrade would be better or headers.. Headers are #1 upgrade for power.