LT1 pulley install
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TECH Resident
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From: Valdosta Ga.
LT1 pulley install I just bought a 34% underdrive pulley off Ebay for $20. It came with no instructions. First off, its made of steel and it seems kinda heavy, is this good? It came with no bolts either so I was wondering if you guys could give me a rundown on the install and what parts I might need. Also, does it replace the whole balancer or does it mount between something? Kinda confused here! Thanks!
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it does not replace anything....you have to pull your harmonic balance off...unbolt the balancer from the hub and pull the balancer off...the underdrive pulley bolts between the the hub and the balancer. it takes a little long bolts. go to auto part store and get correct size..... steel pulleys hurt alot....your gonna need a shorter belt also. most people buy the aluminum pulley
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From: Halfway back on the Highway to Hell...again!
MAKE SURE YOU MARK WHERE THE TRIANGLE ON THE ORIGINAL BALANCER IS!!!.
On the inner portion of the stock balancer/pulley will be a triangle and 2 round nubbs. The triangle is originally to place #1 piston at TDC when it is at 12 o'clock. Just make sure you put it back on to where it came off. Only 3 possibilties.
On the inner portion of the stock balancer/pulley will be a triangle and 2 round nubbs. The triangle is originally to place #1 piston at TDC when it is at 12 o'clock. Just make sure you put it back on to where it came off. Only 3 possibilties.
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From: Halfway back on the Highway to Hell...again!
No...there is a triangle on the stock balancer that will be in the line of the mark on the hub. 3 bolts, triangulated means the balancer can be fitted in 3 ways. The u/d pulley will also go behind the stock pulley/balancer. The new u/d pulley should have a hole or mark where it should be in line with the triangle on the hub or balancer. I can post pics if need be since my LT1 is out of the car right now. I even have a u/d pulley that I don't use.
This is also a balance issue also, every production LT1 was balanced.
This is also a balance issue also, every production LT1 was balanced.
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From: Valdosta Ga.
Thanks guys! I understand now. But, being steel, it weighs a good 10 pounds. Would you guys put this on your car or should I geat an ASP. Wont this just add to the rotating mass? I really dont see it adding any power. Will it make it rev quicker because that always sounds cool? This is going to be a mostly track car so charging wont be a problem so should I use it, or sell it? Thanks! OH, do they make an underdrive balancer for an LT1?
Last edited by moderate Z28; Mar 3, 2005 at 03:07 PM.
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Originally Posted by SAPPER
No...there is a triangle on the stock balancer that will be in the line of the mark on the hub. 3 bolts, triangulated means the balancer can be fitted in 3 ways. The u/d pulley will also go behind the stock pulley/balancer. The new u/d pulley should have a hole or mark where it should be in line with the triangle on the hub or balancer. I can post pics if need be since my LT1 is out of the car right now. I even have a u/d pulley that I don't use.
This is also a balance issue also, every production LT1 was balanced.
This is also a balance issue also, every production LT1 was balanced.
Joined: May 2004
Posts: 1,593
Likes: 267
From: Halfway back on the Highway to Hell...again!
I stand corrected. 
You're right. The time I was first installing my u/d pulley I caught myself before installing all the bolts. 2 line up but the 3rd doesn't. Damn, I just had to out and check...But you're right. See, 15 years of building LT1's and still learn something. I just always knew to line up the triangles from the beginning.
Thanks Snow Dog.
You're right. The time I was first installing my u/d pulley I caught myself before installing all the bolts. 2 line up but the 3rd doesn't. Damn, I just had to out and check...But you're right. See, 15 years of building LT1's and still learn something. I just always knew to line up the triangles from the beginning.Thanks Snow Dog.
yeah there arent off by much, i dont even think it noticable when just looking at it. lining up the triangles is a good idea, but just not necessary. if im not mistaken the triangle on the hub is to point straight up at 12oclock when at TDC on the compression cycle for cylinder 1. i dont have my book in front of me to verify, but i believe thats right.
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From: Valdosta Ga.
Originally Posted by 97bluebird
i would buy a aluminum pulley. yes they do make a underdrive balancer but they start at around 300 dollars.... good luck finding a used one 
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From: Halfway back on the Highway to Hell...again!
Originally Posted by Snow Dog
if im not mistaken the triangle on the hub is to point straight up at 12oclock when at TDC on the compression cycle for cylinder 1. i dont have my book in front of me to verify, but i believe thats right.
My pulley is a March pulley, But me having an Impala, I only need one, F-bodies need 2...crank & alt.
Originally Posted by SAPPER
Yes, that is right.
My pulley is a March pulley, But me having an Impala, I only need one, F-bodies need 2...crank & alt.
My pulley is a March pulley, But me having an Impala, I only need one, F-bodies need 2...crank & alt.
Originally Posted by brandboZ28
I had a March crank and alt pulley on my 93 and got rid of em. Too many problems, not enough(any) gains.
That's my take. I'm just going to leave it as it is. Now if it were a race only car it wouldn't have an accessories except just the alternator
Joined: May 2004
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From: Halfway back on the Highway to Hell...again!
I see what you're saying, Snow dog. ASP makes the u/d pulley / dampner all in one. But when I bought mine (1995) there wasn't anything like that available. Besides, mine has been sitting in my tool box since 96. Wasn't worth anything and was just more of a PITA on the alt., especially when the fans kicked on.
Originally Posted by buffman
That's my take. I'm just going to leave it as it is. Now if it were a race only car it wouldn't have an accessories except just the alternator
