killerIROC

i have a 1988 IROC 5.7 L98 and was curious how beneficial underdrive pulleys would be on my car and any application. I heard the eat belts quick! Any advice!!

Dzaw

Well, first, you're right, they'll chew belts, but then again, any belt system does that at some rate or another.

Next though, you have to understand the tradeoff. You can gain HP (5-15% more HP) by underdriving certain things, but IMHO, you're better off spending your money on something else. With an underdrive kit, your accessories are not turning at the rate they are meant to. Your lights are going to dim, especially at idle, your heat/AC won't blow as hard, and your ignition is going to lose some umph. You can FORGET about a high po sound system, your alternator just won't put out enough juice anymore, and you're just going to eat batteries.

Even worse are the systems that underdrive water pumps, heat is enough of a problem for our cars, let's not get rediculous!

MdFormula350

https://www.thirdgen.org/techbb2/sho...rdrive+pulleys

https://www.thirdgen.org/techbb2/sho...rdrive+pulleys

https://www.thirdgen.org/techbb2/sho...rdrive+pulleys

https://www.thirdgen.org/techbb2/sho...rdrive+pulleys

https://www.thirdgen.org/techbb2/sho...rdrive+pulleys

https://www.thirdgen.org/techbb2/sho...rdrive+pulleys

i ran a search for you..

91B2L

I've got the March 2 pc. pulley. I've had it going on 8 months with no problem in over heating, or battery charging. The down side is ......I didn't feel any more power like I would an exhaust or intake upgrade. I'm sure more hp is there on a dyno.

killerIROC

well a buddy of my has a 2-piece he was gonna sell me for $40 from Mac Performance, but the altenator pulleys is the same size as the Mac pulleys, i would only gain from the crank, which is about 2-21/2 times smaller! But maybe i wont! Thanks!

drdave88

iTrader: (3)

underdrive pulleys will also burn up the bearings in alternators and waterpumps and so on a lot faster. they spin the bearings at such a faster rate of speed that they dont last nearly as long as they were intended to. ive heard this is crap from some people, and ive heard its true from others, if you think about it, it would make sense. IMO, i wouldnt run them.

RICHRAD

I would think the bearings would be less stressed...They are underdriven....right? Would the other pulleys be spining slower because the crank pulley is smaller...I'm new at this ..so someone step in please

vjo90RS8

iTrader: (1)

Yeah, they should be rotating slower since that is the whole purpose of a underdrive pulley set.
I installed an ASP crank pulley and noticed alittle more top end, i have no regrets.

25THRSS

Get the march power and amp series pulleys and you wont have any problems with charging. Underdrive pulleys arent smaller, they are bigger which means they rotate less, with smaller pulleys they rotate more so they wouldnt be underdriven they would be overdriven. Some cars actually run cooler with underdrive pulleys because the water stays in the radiator longer letting it do its job. The slower an accesory turns the more power and less wear although you dont want to go to slow or else things wont function right. Its really a trade off that depends on the car. Just a little info for you guys

vjo90RS8

iTrader: (1)

ok, lets get underdrive pulleys understood. If the crank is rotating at 1000RPMs, then the crank pulley is rotating at the same rate because it is attached to the crank. The small ther crank pulley, the small the crank is going to drive the accessories. BUT, yes, the accessory pulleys are bigger so they rotate less, but the crank pulley is smaller.

25THRSS

wrong, the crank pulley is bigger, smaller would turn faster. Think of it this way....take ure car and put some 20 inch rims with matching tires, now put some 15 inch rims on it and ure gonna turn more rpm with the smaller tires because they turn more times every second than a bigger tire. same principle with underdrive pulleys. ure right about it turning the same rpm as the engine, but the belt will turn less times with a bigger pully vs a smaller one

vjo90RS8

iTrader: (1)

think about it man, the crank is connected to the crank pulley, they have to turn at the same rate right. Its common sense, the smaller the crank pulley, the smaller it drives the other accessories.

vjo90RS8

iTrader: (1)

same rotational velocity, but a smaller tangental velocity (smaller radias), thus, underdriving the accessories, if you dont agree with me on this one, i dont know what to say.

25THRSS

yes ure right it is connected to the crank pulley, but ure thinking is wrong. the bigger the pulley the less times it rotates per minute. if you were to take a 3 inch pulley and put it on and put a mark on it you would see the mark fly around more times than if you put a 3 foot pulley on it. Its just hypathetical. I know a three foot pulley is impossible, i was just tryng to make a point

vjo90RS8

iTrader: (1)

ok, if the crank rotates once, then the crank pulley rotates once, RIGHT?!?!?!?!?!, whether it is 1000000" or 1", you are thinking the wrong way. its physics man, and ive take enough to understand this basic concept.

Justins86bird

For the drive pulley, the larger the pulley, the faster the accessory will spin. For a driven pulley, the larger the pulley the slower that accessory will spin. Underdrive crank pulleys (the drive pulley) are smaller then stock. Because they are smaller, they move less belt per rpm, which in turn slows down how fast the accessories spin.

25THRSS

yes ure right, i am corrected, i was thinking the other way around. thanks for setting me straight

vjo90RS8

iTrader: (1)

Its all good man, we are here to learn, and you just learned something

If i read my old post, i think i was the dumbest car person alive, now i like to think that i am alot more knowledge, but i still have alot to learn, like most of us on the boards.

BaLleRz68

I remember when u didn't know how to change oil.

25THRSS

lol, that was a while ago for me. I consider myself very knowledgable about cars considering i did my first engine rebuild when i was less than 10 years old with the help of my dad. Every once in a while i will earn something like the difference between drive and driven gears which to me now seems pretty obvious, lol. Sometimes my brain doesnt like to function. This board is very helpful when it comes to my third gen and any car really. I learn something new all the time. Thanks guys

gabebandit

I have the March 3 piece aluminum set on my 90 Formula. I can feel a difference with them, it deffinately freed up some power. They have been on for 2 years now and have never thrown a belt. I have no cooling or charging problems. The pulleys slow down you accessories to create power. Also the aluminum is lighter and easier for the motor to turn. If you get any get these or the 3 pc Power pulley set from March.:rockon:

25THRSS

were they the power and amp and are you auto or manual?

vjo90RS8

iTrader: (1)

i think, unless you are going for the nice polished look of the 3 piece March set, just get an ASP crank pulley, i think i paid like 60 for mine. I hear the water pump pulley on the March set is the same size as the stock one, and the alternator pulley doesnt even make much of a difference.

gabebandit

They were the regular set. They work great to me. It's an auto car.

RICHRAD

Well, here's what I think. Not sure of what sizes these pulleys are compared to the stock set-up. But if the crank turns one turn, the crank pulley turns one turn. No matter how big. In the machinist trade, we call the spinning at the diameters,"surface feet per minute". Larger the crank pulley,the more feet per minute it is gonna move the belts in one revolution. So the idea of a larger crank pulley seems to defeat the purpose I guess unless the alt. pulley is way smaller than stock. The deal with excessive belt useage/throwing belts ....wouldn't that be more of belt sizes or belt alignment problems?......

wyclefsirocz

true the belt moves at a slower speed and there for it moves your waterpump, alternator, power steering, etc.. at a slower rate. march pulleys makes too sets. the regular set has a alternator and a crank pulley. the power and amp set hasa smaller crank and a much smaller alternator pulley so you don't put any drain on your battery tan the oem pulleys would.- but you a/c, power steering, and water pump will suffer

my .02

jd13

Have had underdrive pullies on my IROC for 10 years or so now. Times are in my sig. I think they are a good benefit.

Yes, my lights dim slightly at stoplights. Yes, I have a system. Yes, I ran through some altenators, but have had this current one for 3 years now. The only cooling problems I have had was from a leaky radiator hose.



I think that's crap. ;p I'm still on my stock waterpump after 10 years of underdrive pullies. If you have a well taken care of car, and continue to care for it, you will not see any problems with pullies imo.

wyclefsirocz

hey jd13 ur right that state ment is totally wrong. under drive pulleys REDUCE the speed of your water pump and alternator. if they are doing anything, they are saving them!!! but your sufering from loses in coolant flow(get a high flow waterpump), and the alternator, just put a smaller pulley (on the alternator)that they give you that will retain the stock turning ratio of the oem pulleys.
btw y lights dime wit out the pulleys, so whats a loulsy, 2% of power 5amps, come on get a 140amp alternator and you'll neva have anypoblems with pulleys.
my .02

91 z28 350

Jd13 what kind of underdrive pullies do you have ?

RedGTAta1

im trying to understand this as well. Hmm. Im thinking of a bike right now, like a 10 speed. First gear big sprocket easy to turn and move faster at low rpm but spins alot more fast at higher rpm because of higher amount of peddaling, where as 5 gear is a "mid-range" like a stock pulley, and 10th gear being a little harder to get moving but at higher engine rpm and higher speed it would benifit from less stress, like not spinning you feet as hard to work for the same rpm? Let me know if I have this right, thanks
Derek

wyclefsirocz

RedGTAta1 u kinda got it.
stock pulleys are meant to turn the accesorys at right speeds.
when you install a underdrive pulley(they come with the crank pulley and most come with an alternator pulley. some also come with an waterpump pulley too. by installing a smaller crank pulley this will REDUCE the belt speed. thus reducing the rpm of everything else. now the alternator pulley that the kit gives you is alsoo smaller, to bring the speed of the alternator back or close to the stock rpm. and the kits that include the wter pump are usally the billet alumium ones. they give you that pulley so it looks good. it isn't any beter than the stock one. it just gives you that custom look.

the pros-
1- slower turning of the waterpump, power steering, and a/c (if u have it) thus making them turn slower lets your engine make more power do to the strain.
2- less wear on your belt/s.
3-more power
the cons-
1- cooling problem due to less coolant flow
2-a little harder to steer cause of a slow power steering pump
3- ur a/c won't blow as hard when its on compared to the stock pulleys
4- if u buy the wrong kit, your electrical system will not have enough juice. (or if u don't install it at all)

your gonna have to look at your case and decide if they are for you.
inmy case- i got a high flow water pump and a 100amp alternator, so i'm not affected.

vwdave

If you are that worried about overheating your car, get a performance waterpump that outflows stock to compensate for the pulleys.

I dont know about you guys, but I have smoked 3 batterys and 3 alternators, so I cant imagine killing them faster.

wyclefsirocz

what pulleys do u have and did u install the alternator pulley,
one problem here two possible ideas
1- wrong pulleys or installed incorrectly
2- a problem somewhere else

vwdave

When I get time......

wyclefsirocz

didu install them correctly(installed the alternator pulley too), or did u buy the wrong ones, which ones did u buy

or if u have a large stereo tht could be it too.

vjo90RS8

iTrader: (1)

i installed an ASP crank pulley and have not noticed any changes in cooling and no significate changes in alternator voltage, at idle the meter does drop, but only to around 12 volts.

Larry Dunlap

Maybe somebody said it and I missed it, but do you have to run a special belt then? What size belt do you run. I looked at the two piece steel March set for about $70 compared to the 3 piece March aluminum set for about $170. Big difference for just show. I guess the aluminum would be a hair lighter but still,,,,

vwdave

Maybe call summit or march and ask them?

wyclefsirocz

you do need a new belt, i dunno the size

bubafett

I have actual experience!

It works! Car had more torque. would spin tires going into 3rd with T5. would not do so before. Car felt more responsive.

I have had an underdrive pully since 1991.

Broke first belt in 1999.

Car never over heated.

Power steering felt beeter due to more effort.

I bought it from, I forget, but I only replaced the drive pulley. The one on the crank.

No need to replace any other pulleys.

These are the facts Jack