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underdrive pulley?

This is a discussion on underdrive pulley? within the External Engine forums, part of the LSx Technical Help Section category; what exactly is an underdrive pulley and what does it do for your performance and also i have a cam, ...

  1. #1
    408 ci + 4000 stall = fun lancesT/A's Avatar
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    underdrive pulley?

    what exactly is an underdrive pulley and what does it do for your performance and also i have a cam, intake, full exhaust and a hypertech chip what would an underdrive pulley do for me and would it be worth buying?

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    Junior Member freakinstreakin's Avatar
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    I know the concept of it, but would not be comfortable explaining. I too would like to know how beneficial they are to our cars???

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    Veteran 0rion's Avatar
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    In a nutshell an underdrive pulley is smaller and lighter. It cuts down on parasitic losses and lets the engine rev faster.

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    408 ci + 4000 stall = fun lancesT/A's Avatar
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    so what pulley does it replace and how hard is it to install

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    Veteran 0rion's Avatar
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    the crank pulley. Fairly easy swap. Just use a 3 jaw puller to get the old one off and then put your new one back on. Some people use the old bolt to pull the new pulley onto the crank but that's a risky move because you take the chance of pulling the threads out of the end of your crank. I bought some metric all thread, washers, and bolts and made an installer tool that removes that chance. Pretty simple and if you decide to do the swap PM me and I'll explain the all thread deal a little better.

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    Junior Member freakinstreakin's Avatar
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    What kind of gains are seen with the pulley?

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    408 ci + 4000 stall = fun lancesT/A's Avatar
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    Quote Originally Posted by 0rion View Post
    the crank pulley. Fairly easy swap. Just use a 3 jaw puller to get the old one off and then put your new one back on. Some people use the old bolt to pull the new pulley onto the crank but that's a risky move because you take the chance of pulling the threads out of the end of your crank. I bought some metric all thread, washers, and bolts and made an installer tool that removes that chance. Pretty simple and if you decide to do the swap PM me and I'll explain the all thread deal a little better.
    thanks alot i here that it would be a pretty good mod because it is fairly cheap and i should atleast feel a little difference in throttle response. and dont worry when i decide to do i will ask you a shit ton of questions.

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    Member transws6am00's Avatar
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    Quote Originally Posted by freakinstreakin View Post
    What kind of gains are seen with the pulley?
    i second that ive seen sites that claim 10-15 horses out of it but is that true?

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    Pathelogical Liar BlackLT1Z28's Avatar
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    I doubt you'll get 10-15hp out of a pulley swap. Maybe 5, but the most common difference I hear is better throttle response.

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    SS#430 1 of 74 7camaro7's Avatar
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    with the pulley mod do you NEED a tune?

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    Member Huskerz1's Avatar
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    Quote Originally Posted by 7camaro7 View Post
    with the pulley mod do you NEED a tune?
    I wouldn't think so. Most pulley mods are done in conjunction with a cam swap. The crank pulley NEEDS to come off for that. I had the pulley done with my cam kit. You can definitely tell the quicker revs and throttle response.

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    Double Tap Heartbreak1's Avatar
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    Quote Originally Posted by 7camaro7 View Post
    with the pulley mod do you NEED a tune?
    Not unless your camming it at the same time. Be really nice to hear a concrete number on tq and hp differences. Im told alot of times that its good for a 5% increase in all around power.

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    Member Bandit1's Avatar
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    doing underdrive pullies also slows downs ur accessories like the power steering

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    King 0f n00bz shady milkman's Avatar
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    Quote Originally Posted by Bandit1 View Post
    doing underdrive pullies also slows downs ur accessories like the power steering
    yea but your alt. ect pullies spin too fast anyways so it really doesnt hurt them..unless you have a huge system ect.

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    King 0f n00bz shady milkman's Avatar
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    make sure if you get a UD pulley that you get one with harmonic dampening. if not then eventually the vibrations will cause a cracked crank

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    Member Bandit1's Avatar
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    Quote Originally Posted by shady milkman View Post
    yea but your alt. ect pullies spin too fast anyways so it really doesnt hurt them..unless you have a huge system ect.
    good point

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    King 0f n00bz shady milkman's Avatar
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    blacker than wesleysnipes
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    Quote Originally Posted by Bandit1 View Post
    good point
    thanks

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    also UD pulleys, if more then one installed, ( full set of UD pulleys ) being the crank,AC if you have it, power steering, alt, and such can cause overheating issues if you had to sit in traffic for too long, thus for you may need a bigger radiator 4core alum radiator would do the trick, but if your only doing the crank pulley you won't have to worry about it.

  19. #19
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    underdrive pulleys and harmonic ballancers

    i'm confused. are harmonic balancers separate from underdrive pulleys, or are they underdrive pulleys that have just been constructed a certain way?

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    the harmonic balancer is the crank pulley, the biggest one on there or atleast it should be, make sure to get dampening with it too

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