underdrive pulleys on the way

91foxhatch5.0 · May 26th, 2007, 09:39 AM

i ordered some mac underdrive pulleys...theyre the black ones nothin special...what kinda gains can i expect from this...and wat size nut is the alternator pulley

TurboLX · May 26th, 2007, 10:22 AM

maybe a good 5hp

neverfastenough1 · May 26th, 2007, 10:25 AM

Top five questions about underdrive pulleys.
Just remember they are selling them though.

http://www.marchperf.com/underdrive2.html

chadjones99 · May 26th, 2007, 06:37 PM

i started to have eletrical problems after i got some years ago.

tording92lxnotch · May 27th, 2007, 09:08 AM

Originally Posted by chadjones99

i started to have eletrical problems after i got some years ago.

I seriously doubt they are related. The 92 notch I have now is my 2nd mustang in the past 5 years with underdrive pullies and I have never had an issue. If your going to run the alt underdrive pulley however, I highly suggest you do the 3G alt upgrade. Its pretty cheap to do and your lights will no longer dim at idle. This would be the only thing that caused electronics to act funny probably, not enough voltage to operate them properly. Just do the 3G upgrade, trust me.

chadjones99 · May 27th, 2007, 09:33 AM

what is the 3g upgrade >?

tording92lxnotch · May 27th, 2007, 09:46 AM

Originally Posted by chadjones99

what is the 3g upgrade >?

The stock fox body mustang has a wimpy 75 amp alternator. Its barely big enough to power your stock stereo and headlights. Once you put underdrive pullies on it, this will get even worse because your spinning the alternator even slower. You can get an alternator from a 94-95 GT or V6 mustang out of a junkyard or from like autzone. These are upgraded 130 amp alternators to elminate the problem of not having enough power. They are pretty much a direct bolt in with just a little bit of clearancing on the stock bracket where the alternator slides in. You also will want to run a new 4 ga power wire from the post on the back of the alternator to the starter solenoid over on the driver side fender to help carry the extra power. The stock wiring is not big enough to carry it. Its a cheap upgrade and you won't be sorry you did it. If you can find an alt from a junkyard for 30 or 40 bucks your looking at 50 or 60 bucks for the entire project. Then after this is complete you can run you underdrive pulley and run an electric fan with no problems.

91foxhatch5.0 · May 29th, 2007, 09:42 AM

would it be defeating the purpose if i dont run the alternator pulley on it..would i still see some gains?

ryans88gt · May 29th, 2007, 01:11 PM

Originally Posted by tording92lxnotch

Originally Posted by chadjones99

what is the 3g upgrade >?

You also will want to run a new 4 ga power wire from the post on the back of the alternator to the starter solenoid over on the driver side fender to help carry the extra power. The stock wiring is not big enough to carry it. .

Just to let everyone know, it is a really really good idea to put a fuse between the alternator and the solenoid if you are going to upgrade your alt wiring. Autozone sells 175 AMP fuses cheap. Here is the reason, the sock wiring has a fusable link that is designed to fail, but if you replace this with a 4 ga wire you can have some problems. If your alternator diodes go bad and result in a ground to the alt case you are suddenly connecting the positive side of your battery directly to ground with no fuse or fusable link. This could easily result in a fire or small battery explosion. It can happen, that is why a fusable link is designed into the stock wiring.

fogged306 · May 29th, 2007, 03:54 PM

Originally Posted by ryans88gt

Originally Posted by tording92lxnotch

Originally Posted by chadjones99

what is the 3g upgrade >?

You also will want to run a new 4 ga power wire from the post on the back of the alternator to the starter solenoid over on the driver side fender to help carry the extra power. The stock wiring is not big enough to carry it. .

Just to let everyone know, it is a really really good idea to put a fuse between the alternator and the solenoid if you are going to upgrade your alt wiring. Autozone sells 175 AMP fuses cheap. Here is the reason, the sock wiring has a fusable link that is designed to fail, but if you replace this with a 4 ga wire you can have some problems. If your alternator diodes go bad and result in a ground to the alt case you are suddenly connecting the positive side of your battery directly to ground with no fuse or fusable link. This could easily result in a fire or small battery explosion. It can happen, that is why a fusable link is designed into the stock wiring.

x 1,000,000,000. I actually had an installer at my shop not do this and the car caught fire because the wire was touching the manifold and it burned through, shorted out, and burnt the car to the ground.

Luckily the adjuster was an idiot and blamed the problem on the hi-amp alt. we installed at the same time and the kid got to keep his job.

ryans88gt · May 29th, 2007, 10:19 PM

Yeah, I bought my 3g upgrade from a reputable alternator company. I asked them about needing a fuse or fusable link.

They actually told me there was no purpose for it. I asked what if the wire grounded out. They said that "never happens". Good thing I did some research, before the installation.

8t6gt · May 29th, 2007, 10:30 PM

I wouldnt worry about the charging I just put the march set on my 86 gt and no difference in charging they have been on for almost a month.

They wont make a difference unless you have a huge stereo system that you need to have at a high volume at idle

mobius · May 29th, 2007, 10:45 PM

i know a guy who got a set and then 5 years later, bam, herpes.
j/k

fogged306 · May 30th, 2007, 01:20 AM

JonnyB · May 30th, 2007, 07:45 PM

I recently purchased a 89 5.0 that has underdrive pulleys and I hate how they slow the alternator making my lights dim. Would I be able to replace just the alternator pulley to fix this or would I have to replace all three pulleys?

Tony_90fox · May 30th, 2007, 10:38 PM

you can put the stock alt pulley on there and keep the other two on there...Many people do that....I have no charging problems though.

tording92lxnotch · May 31st, 2007, 03:46 PM

Yes, puting a fuse inline in that 4 ga wire is a very good idea. That is how I have mine setup, I forgot to mention it in my previous post. Good catch guys.

8t6gt · May 31st, 2007, 05:59 PM

I dont have any problems with dimming lights

I dont know why everyone does ive never personaly met anyone that had problems with them

ryans88gt · May 31st, 2007, 11:33 PM

Originally Posted by 8t6gt

I dont have any problems with dimming lights I dont know why everyone does ive never personaly met anyone that had problems with them

Mine dim even with the 3g upgrade. It depends greatly at what your car idles at. At 800 rpm my lights dim and my charge gauge drops a few notches, but by 900 rpms it's right back at full charge. I don't know what brand of underdrives I have on there, but the crank pulley is smaller than the water pump pulley...

91foxhatch5.0 · June 4th, 2007, 08:11 AM

finally got them in on friday and started to put them on saturday and the pulley on the alt. would not come off so im takin it somewhere today and gettin it took off and finishing up the install

May 26th, 2007, 09:39 AM	#1
91foxhatch5.0 Regular 1991 mustang lx 5.0 14.5@92 Join Date: Nov 2006 Location: welcome, nc Posts: 131	underdrive pulleys on the way i ordered some mac underdrive pulleys...theyre the black ones nothin special...what kinda gains can i expect from this...and wat size nut is the alternator pulley

May 26th, 2007, 10:22 AM	#2
TurboLX IT'S TURBO TIME 1990 Mustang LX Turbo Join Date: Oct 2006 Location: NY Posts: 8,651	maybe a good 5hp __________________ *Put up, Shut up, Line Up And Get Beat Up!!!*

May 26th, 2007, 10:25 AM	#3
neverfastenough1 Hardcore Enthusiast 2002 Mustang GT Join Date: May 2007 Location: Savannah, Ga Posts: 1,345	Top five questions about underdrive pulleys. Just remember they are selling them though. http://www.marchperf.com/underdrive2.html __________________ 2007 Explorer Sport Trac, 292 HP, Stock 2002 Mustang GT

May 26th, 2007, 06:37 PM	#4
chadjones99 Regular Join Date: Aug 2006 Location: Tonopah,az Posts: 86	i started to have eletrical problems after i got some years ago. __________________ 1986 stang ,Edelbrook intake, aluminum heads, E303 cam ,70 MM throttle body ,24lb injectors ,373 gears , 10:1 pistons set up,no cats , flowmaster mufflers , short shifter , 255 fuel pump , smog pump delete , A/C delete , Aluminum Radiator , MAF convertion

May 27th, 2007, 09:33 AM	#6
chadjones99 Regular Join Date: Aug 2006 Location: Tonopah,az Posts: 86	what is the 3g upgrade >? __________________ 1986 stang ,Edelbrook intake, aluminum heads, E303 cam ,70 MM throttle body ,24lb injectors ,373 gears , 10:1 pistons set up,no cats , flowmaster mufflers , short shifter , 255 fuel pump , smog pump delete , A/C delete , Aluminum Radiator , MAF convertion

May 29th, 2007, 09:42 AM	#8
91foxhatch5.0 Regular 1991 mustang lx 5.0 14.5@92 Join Date: Nov 2006 Location: welcome, nc Posts: 131	would it be defeating the purpose if i dont run the alternator pulley on it..would i still see some gains?

May 29th, 2007, 10:19 PM	#11
ryans88gt MM Fanatic Join Date: May 2007 Location: Bloomington, IL Posts: 3,563	Yeah, I bought my 3g upgrade from a reputable alternator company. I asked them about needing a fuse or fusable link. They actually told me there was no purpose for it. I asked what if the wire grounded out. They said that "never happens". Good thing I did some research, before the installation. __________________ 89 LX 515 hp 497 ftlbs 11.3 @ 125 mph 88 GT 11.4 @ 118

May 29th, 2007, 10:45 PM	#13
mobius Newbie Join Date: May 2007 Posts: 19	i know a guy who got a set and then 5 years later, bam, herpes. j/k

May 30th, 2007, 01:20 AM	#14
fogged306 Hardcore Enthusiast 89 GT Join Date: Apr 2007 Location: Did you get that thing I sent you? Posts: 1,189

May 30th, 2007, 07:45 PM	#15
JonnyB Newbie Join Date: May 2007 Posts: 17	I recently purchased a 89 5.0 that has underdrive pulleys and I hate how they slow the alternator making my lights dim. Would I be able to replace just the alternator pulley to fix this or would I have to replace all three pulleys?

May 30th, 2007, 10:38 PM	#16
Tony_90fox MM Fanatic Join Date: Jun 2006 Location: Bowling Green, KY Posts: 3,621	you can put the stock alt pulley on there and keep the other two on there...Many people do that....I have no charging problems though. __________________ 393 dropping in a foxbody near you, very very soon Military Crew E-3 Combat Engineer

May 31st, 2007, 03:46 PM	#17
tording92lxnotch Regular Join Date: Apr 2007 Posts: 165	Yes, puting a fuse inline in that 4 ga wire is a very good idea. That is how I have mine setup, I forgot to mention it in my previous post. Good catch guys. __________________ 92 notch--Shorty headers--Pro 5.0--3G alt--U/D pullies--A/C delete--190 LPH Walbro FP--Compucar N2O kit--FMS alum D/S--Taurus fan--Weld Draglites--Mallory 685 ign Box--dccontrol fan controller 13.0 - 108 mph - 1.9 60' - 90 shot N2O and 175k on the clock

June 4th, 2007, 08:11 AM	#20
91foxhatch5.0 Regular 1991 mustang lx 5.0 14.5@92 Join Date: Nov 2006 Location: welcome, nc Posts: 131	finally got them in on friday and started to put them on saturday and the pulley on the alt. would not come off so im takin it somewhere today and gettin it took off and finishing up the install

Threads Similar to: underdrive pulleys on the way
Thread	Thread Starter	Forum	Replies	Last Post
BBk underdrive pulleys	03Gtmustang	99-04	6	September 26th, 2007 03:46 PM
when you buy underdrive pulleys	matfernan1	99-04	21	September 26th, 2007 01:55 AM
Underdrive Pulleys	justinsstang	V6 Mustangs	6	February 24th, 2007 04:14 AM
Underdrive Pulleys	97stanger	V6 Mustangs	26	February 22nd, 2007 11:29 PM
Underdrive Pulleys	jerb43	96-98	5	October 24th, 2006 12:05 PM

All times are GMT -4. The time now is 02:50 PM.
Contact Us - Modded Mustangs - Top
Modded Mustangs is ©2005-2008, All Rights Reserved, And is Not Affiliated with Ford Motor Company. Forum is powered by vBulletin ©2000 - 2008, Jelsoft Ent. Ltd. & SEO by vBSEO 3.1.0 ©2007, Crawlability, Inc.