Thinking about underdrive pulleys..

foxbodyrules · Dec 4, 2004

I'm thinking about buying a set of underdrive pulleys for my 91' GT. First off, what are the best kind? Now the main reason for the post is after doing a search on here i saw people sometimes had trouble with their alternator when they installed underdrive pulleys. I have no idea what alternator i have on there, but i just had the vehicle fully inspected, so everything is fine. My question is.. will the underdrive pulleys cause any problems? Cause if they will then i'll think about skipping this. My upgrades are:

3.55's
flowmaster catback
shorty headers
catted h
ford racing valve covers
upgraded spark plugs/wires
aluminum radiator
bbk cold air intake
pro 5.0
tremec transmission

So, which u/d's and would they help? thanks a lot.

fiveoboy02 · Dec 4, 2004

If you don't have a lot of electrical accessories, such as an electric fan and a big stereo, you should be OK with the stock alternator. Mainly the problem is that the alternator won't charge well at idle because it is spinning slower. At above-idle engine speeds it isn't a problem.

Michael Yount · Dec 4, 2004

It's near impossible to predict what your experience with u/d's will be. You'll just have to try them and see. If your car is a fox body and has the stock alternator it's a 65A unit and pretty marginal for even the stock electrics. And as stated above, the u/d's slow the alternator down a bit. Similar issues may occur on the cooling front - since water pump and mech. fan are slowed down, sometimes people experience cooling problems at low speed. No way to predict - only by trying will find out what's gonna happen to yours. If you have lots of added electrics, or if you live in a part of the country that gets really hot in the summer, and/or drive your car with the a/c on in a lot of stop and go traffic - those factors increase the odds of your having difficulties.

I removed them from mine to solve summer overheating in traffic, ineffective a/c in traffic, charging issues and a howling power steering pump.

Darkhorse845 · Dec 4, 2004

I highly recommend ASP pulleys!

jb89coupe · Dec 4, 2004

I have asp's on my car (see sig) - no problems. I can't say I really felt a difference in acceleration when I installed them, but it revs much quicker and seems a little more responsive with the underdrives. Takes all of a half hour to get them on too.

Edit: I have a stock altenator but I bypassed the a/c and smog pulleys. I also have no radio.

Michael Yount · Dec 4, 2004

Here's the thing to remember foxbody - an auto tranny'd, vert in Houston sluggin it out in bumper to bumper in August with the a/c on high and the original radiator puts an entirely different load on the cooling/charging system than a weekend cruiser light-weight notch with a T5, a big aluminum Griffin radiator, no a/c in a rural area in New England. Be careful about any posting that says 'they worked great on mine - they'll be fine on yours'. Also, I've seen a couple of dyno runs in mags on pulleys. The majority of their gain comes above 3500 rpm - a range rarely accessed on the street in normal driving. If you want something that's guaranteed to help your car's performance that won't cost much more than pulleys, send a PM to tmoss here or at Corral and see about replacing your lower intake with one of his ported stockers. It'll improve power/torque across the rev range with no downside in terms of drivability or other potential issues.

86StangLX · Dec 4, 2004

I've been running BBK underdrives for a couple years now and didn't run into any problems until I installed a big stereo with a sub. It ran fine for a quite some time like that, then the alt. finally went out. I'm also running an Optima RedTop. I've since switched to a Powermaster 140amp alternator and it's all good now. I'm also running aftermarket foglights. The car doesn't like to idle for long periods of time, or it struggles to charge. Other than that, it does just fine. Also, I'm running a stock pulley on the alternator which makes it spin a little faster. I've been all over the map with this pulley/electricity/charging issue. I can only offer my advice, and that would be upgrade your alternator while you're at it. Especially if you're running a lot of electrical accessories.

foxbodyrules · Dec 4, 2004

Well I am in Maryland, summers can get pretty hot so i guess i'll just skip the pulleys. Thanks for the advice on porting the intake. I'll think about it. In terms of alternators, if in the future i were to upgrade, what would be a good but reasonably priced alternator?

deftsound · Dec 4, 2004

funny how you mention houston traffic when you live in tn, guess houston is famous for that, i was thinking of getting ud's too but i live in south texas

Michael Yount · Dec 4, 2004

I lived in Houston for 15 years prior to moving to east TN.

I got my alternator and starter from Pa-Performance - www.pa-performance.com. Not the least expensive, but in my opinion, the best value. All new components, quality stuff, idiot proof instructions, great customer service. Their 95A alternator goes on without having to cut/grind the bracket.

Kdubslugga · Dec 4, 2004

I have steel BBKs, and i think i felt a bit of difference with them. I do notice the volts drop at idle but thats about it. No cooling problems here.

ninety15.0 · Dec 5, 2004

i got a set for free and decided to throw them on there for fun just to see if i would experience any of the problems. I did not install the alt pulley, just the water pump and crank. I did feel a noticable difference in how quickly the car revved but no real big seat of the pants improvement. They are cheap, if they work, hey every little bit helps, and if they dont it was only 100 bucks. good luck

Allforspeed · Dec 5, 2004

on my particular car i now have to replace the battery every 6 months which sucks and i cant have the stereo, headlights and wipers on at night or the stereo cuts out every time the wipers go on , but its a pretty proven 6-8 HP, so i just got a 3G 140 amp alternator off of ebay brand new and installation is really easy, installing the ramcharger fan when i get a minute so might as well upgrade the alternator, new ones are more reliable anyway, cheap and better, just upgrade now when you do pulleys, you'll be happy later

deftsound · Dec 5, 2004

yea im probably gonna get some here pretty soon, any brand yall recommend or are they all pretty much the same? Also, are the pulleys bigger then the stock ones? IF so i bet that serpantine belt is a bitch to get back on

Michael Yount · Dec 5, 2004

There should be enough 'range' (look closely at the face of the belt tensioner) to accomodate the different sized pulleys. It takes a smaller drive pulley (the one on the crank) to slow down accessories. Most kits also have slightly smaller water pump and alternator pulleys to slightly speed those two back up to try and help not cause cooling or charging issues. Remember - smaller drive pulley (crank) slows driven accessories down. Smaller driven pulleys (pump, alt, power steering/a-c) speed those accessories back up. Larger driven pulleys slow those accessories down. The change in speed is directly proportional to the change in diameter of the pulley. So, if you change from a 2.5" diameter alternator pulley, to a 2" diameter, you will speed up the alternator by 25%.

They are not all the same - check with the manufacturer for details. Some are steel, some are aluminum. And different diameters are used. The FRPP pulleys claim to reduce the water pump speed by 11%, the alternator speed by 22% -- and they also come with a big WARNING -- "Engine cooling will be reduced". Other kits make other claims.

04sleeper · Dec 5, 2004

I run a 4 inch ASP crank pulley.

an overdrive alternator pulley.

and a stock water pump pulley.

I lived in South Florida for 20 years and now in Texas and don't have any issues with this setup.

When I feel like going to the track I put on a 3 inch Race crank pulley and it is ok when I do not run the A/C and such.

maverick0716 · Dec 5, 2004

I run March "hp pullies". I definitly noticed a difference on my car. I've had them on my car for 2 years and my battery has gone dead once. I've never had any cooling problems.

93tealstang · Dec 5, 2004

89sleeper said:
I run a 4 inch ASP crank pulley.

an overdrive alternator pulley.

and a stock water pump pulley.

I lived in South Florida for 20 years and now in Texas and don't have any issues with this setup.

When I feel like going to the track I put on a 3 inch Race crank pulley and it is ok when I do not run the A/C and such.

Without running a bigger water pump pulley, I'd think there wouldn't be much gain with your setup since your not really reducing anything to make power. It does seem logical since your not loosing colling or charging abilities but how much of gain do you think it might be worth over a full set of underdrives?

super302 · Dec 5, 2004

I AM SELLING MINE, NEVER INSTALLED, BRAND NEW!!!

PM ME IF INTERESTED

93tealstang · Dec 5, 2004

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