Underdrive Pulleys

[#1stunner]

I am putting in an underdrive pulley into a 87 350ci. What is the best air wrench to loosen and tighten the pulleys with? How much FT-Lbs of torque will I need? If you have done this mod please respond. Thanks

 

[#1stunner]

I ended up getting a simple northern tool air wrench $50. It worked really well, got the job done in less than 1.5 hrs. The pulley was from TPIS. And came w/o a belt which was purchased at Checker auto for $40. The pulley system was really easy to put in other than moving the radiator hose out of the way to make room for the air wrench. Now the car pulls really strong. Full throttle @ 20 mph= ONE really big Drift. Tires didn't grip at all, time for some better ones. Easy mod for little money.

 

[Mad-Mic]

I ended up getting a simple northern tool air wrench $50. It worked really well, got the job done in less than 1.5 hrs. The pulley was from TPIS. And came w/o a belt which was purchased at Checker auto for $40. The pulley system was really easy to put in other than moving the radiator hose out of the way to make room for the air wrench. Now the car pulls really strong. Full throttle @ 20 mph= ONE really big Drift. Tires didn't grip at all, time for some better ones. Easy mod for little money.

did you go with the 2 piece kit? if so i'm waiting on mine to come from eckler's. i still have to install my AIR pump elim kit and the pulley kit. i think i am just going to do the crank pulley and not the alt pulley.

what is the part # for the belt you got?

thanks!

 

[#1stunner]

I used a dayco Part# 5060860. You'll need two people for getting the belt on. One for getting it off if you cut it (bad idea). The other person will hold down the belt tensioner with a big stick 2x2x2". While the other takes off and puts on the new belt. I replaced the alternator and crankshaft. Only the alternator needed the air wrench and wd-40 to put back on. The crankshaft needed and socket set with extensions. I recommend taking out the power steering brackets to get an angle on the Alternator pulley.

 

[Mad-Mic]

thanks man!

 

[Vettefan87]

I have been thinking about getting underdrive pulleys for my car. Is there any brand better then the other, or are they all about the same? Thanks


Justin

 

[Edmond]

What gains could you expect from the underdrive pulleys?

 

[vetteboy86]

I am curious too. I have seen these many places.? I would like to know spending the money would be justified with a gain in performance.


Craig

 

[taegdh]

The idea of the underdrive pully, is that there is less parasitic loss of power in driving the accessories by using a smaller pulley on the crank and slightly larger pulley on the alternator, (and where legal eliminating the a.i.r. pump). The only down part is the alternator may not be charging "Fully" at or near idle. You have to keep the revs up to keep it going at full charge.


I may be mistaken but, in a Vette, (or any other type of hot rod), isn't that the object? More Power, Freely Revving V-8 AMERICAN Muscle!!!!!

I'd hate to think I've been mistaken all these years.

 

[Mad-Mic]

guys that just change out the crank pulley see .1 and 1 mph more in the 1/4 mile. every little bit counts

 

[vetteboy86]

Mic,

Just by changing the crank pulley you saw those gains? So what is the purpose of the two and three pulley sets? I guess to get more money, but honestly is there more to be gained?

Craig

 

[Bob Yates]

Hey guys on my 81 I changed the alt. , water pump and crank pullies and was amazed at the difference. It seemed to pull strong. I notice I started giving those rice burners a run for their mufflers....Now that I own a C4 I'm going to do the same mod and remove A.I.R. pump and install true dual exhaust. Where I live we just got rid of our V.E.T. testing....Watch out 60's for a rerun of musle cars.....Bob Yates

 

[#1stunner]

When you change your pulley set like the ones Mic's and I have, you increase the number of rotations at the crank and alternator, through reducing the size of the pulley. It has been reported that on a 1990 corvette you can take .4 off your 1/4 mile! Exactly what every c4 needs more speed!

 

[vetteboy86]

I am really interested in doing this. However I would like to make a bracket instead of buying one. If I remember right they are pretty salty just for a pulley bracket. How much work is involved with removing the air pump?


Craig

 

[WhalePirot]

another side, not popular

guys that just change out the crank pulley see .1 and 1 mph more in the 1/4 mile. every little bit counts

Cool for all-out. at the track.

On the street, I saw a very uncomfortable increase in steering assist when parking, which will keep those pulleys off my cars. Discharging at idle is another, but multi-pulley setups can ensure sufficient alternator speed.

Did you ever spin the air pump and see how little power it takes? In my book, the potential for Federal fines for disabling SMOG gear speaks much louder than the miniscule power saved. Heck, the alternator saps much more power; why not run without IT for that extra 'racer's edge'?

 

[Bob Yates]

I wondered how the feds can catch no air pump on my ride when they can't catch a camel jockey stealing an airplane.....as far as the pump taking power,I just like a cleaner engine compartment. Taking that junk off has to make the engine a little cooler in temp and looks.....I'm a little tired of people thinking that cars are our air's worst enemy anyway...We've given up leaded fuels and R12 for the treehuggers... Take off the pumps, put on the duals and the pullies and anything else we want....Just do it .....Bob Yates

 

[Mad-Mic]

Mic,

Just by changing the crank pulley you saw those gains? So what is the purpose of the two and three pulley sets? I guess to get more money, but honestly is there more to be gained?

Craig

Craig,

i haven't done the mod as of yet. been working too many hours at work and haven't had the time. hopefully this week i'll be able to do it along with the air pump.

i've watched what others did and am putting my knowledge and what others have done to achieve quick times out of stock L98 C4's. most of this applies to LT1 also like the pulleys.

like WhalePirate said though, your altinator won't charge under 1000 rpm or so. mine is a weekend car only and i am looking for all the HP i can find so i can run 12.50's with a stock L98 motor, stock 1600 stall, 2.59 gears. my goal is 12.70 or better on the stock motor/stall/gears setup then start to mod it with my other parts. as the car is running and the bolt on's i'm doing i think the car in cool air and great DA will run 12.5x maybe.

come on late october! be dry and cool

 

[Mad-Mic]

Cool for all-out. at the track.

On the street, I saw a very uncomfortable increase in steering assist when parking, which will keep those pulleys off my cars. Discharging at idle is another, but multi-pulley setups can ensure sufficient alternator speed.

Did you ever spin the air pump and see how little power it takes? In my book, the potential for Federal fines for disabling SMOG gear speaks much louder than the miniscule power saved. Heck, the alternator saps much more power; why not run without IT for that extra 'racer's edge'?

thats all fine and dandy. i will keep my car with in the testing standards. when i do my other motor it will have a cat.

you do realize california was looking to change the laws to a non visual check right? as long as it passes no questions asked? too bad they didn't do it because you can tune a mildly modded motor with in testing standards as long as you don't go cam crazy along with compression crazy.

you know thats not a bad idea! run a small electric motor to the alt that will spin it 2000 consecutive rpm to keep it charged with a v-belt thats 7 more hp!

hehe bracket guys do that with the water pumps alot of the time...