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"Suck my unit"
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Discussion Starter #1
Hey guys. Well after my crank pulley took a plunge I had to replace it asap, so I was stuck with ordering a underdrive pulley off of ebay. Now, with the stock pulley it is harmonically balanced by a piece of rubber. People said they have thrown codes with the UD pulley because it vibrates slightly causing the CAS to go off. I was thinking, since the stock has rubber why not add some to the underdrive pulley. Before bolting the pulley on, do you think it would benefit if I put on a rubber washer? In theory Im thinking it would absorb some of the vibrations just as the rubber does on the stock pulley.
 

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Well. Where you are coming from does make sense in theory but heres the deal. The pulley on a crankshaft can sometimes be called a harmonic balancer. These are INTERNALLY balanced. If you check out a fluidampr the reason they are superior is because they have a viscous silicone inside them which dampens vibrations. I don't think that fluidampr makes one for this engine but an unbalanced pully can cause vibrations and stress on the crankshaft which in result can cause excessive play in thrust bearings and crankshaft endplay.
As far as keeping the stock pulley. On the 6g72 I would defiantly keep the stock pulley just by looking at it you can see for sure that it is internally balanced and if not internally balanced it is weighted to work with the 6g72 There is reasons that the engineers who designed this engine did they things they did. Nobody has seen any positive experiences from using these said " Performance pulleys"
BTW you would be better off with no washer then putting on a rubber one. A rubber washer will definatly create a weakpoint which will eventually vibrate shit loose. Throw all the belts off and at 2000 rpms it could definatly either break the bolt or the pulley.
 

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"Suck my unit"
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2,927 Posts
Discussion Starter #3
Then I guess Im just going to bolt it on without anything and use it until I find a deal on a stock pulley. Thanks.

Oh and does anyone know the size of hte belt you need? Its a Unorthodox Racing knockoff.
 

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My snail is bigger!
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1,154 Posts
Well. Where you are coming from does make sense in theory but heres the deal. The pulley on a crankshaft can sometimes be called a harmonic balancer. These are INTERNALLY balanced. If you check out a fluidampr the reason they are superior is because they have a viscous silicone inside them which dampens vibrations. I don't think that fluidampr makes one for this engine but an unbalanced pully can cause vibrations and stress on the crankshaft which in result can cause excessive play in thrust bearings and crankshaft endplay.
As far as keeping the stock pulley. On the 6g72 I would defiantly keep the stock pulley just by looking at it you can see for sure that it is internally balanced and if not internally balanced it is weighted to work with the 6g72 There is reasons that the engineers who designed this engine did they things they did. Nobody has seen any positive experiences from using these said " Performance pulleys"
BTW you would be better off with no washer then putting on a rubber one. A rubber washer will definatly create a weakpoint which will eventually vibrate shit loose. Throw all the belts off and at 2000 rpms it could definatly either break the bolt or the pulley.
Do you realize that "internally balanced" refers to the crankshaft and reciprocating mass and not the crank pulley itself?
 

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"Suck my unit"
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Discussion Starter #5
Do you realize that "internally balanced" refers to the crankshaft and reciprocating mass and not the crank pulley itself?
Yea I saw that too. Internally balanced means just that, the engine is internally balanced. I had a 3000GT before and I know that a couple of my buddies from the club had lightweight pulleys and it didn't have any ill effects. Our engines do not rely on the crankshaft pulley to balance things out, all it does is get rid of excess vibrations, hence why theres a piece of rubber in the middle of the pulley. Thats the only reason I wanted to put a rubber washer between the pulley, to take out some of the vibrations because of the CAS. But he made a good point with it possibly unscrewing itself becaue of the rubber washer.
 

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My snail is bigger!
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Well, the 6G72 is indeed internally balanced. I just had mine rebuilt and balanced with a lightweight aluminum flywheel and crank pulley. You should realize that these items will change the balance of your engine slightly and should be factored in when rebalancing an engine.

However, I see no mechanical complications from running a lightweight pulley on an internally balanced engine.
 

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C&O
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As far as keeping the stock pulley. On the 6g72 I would defiantly keep the stock pulley just by looking at it you can see for sure that it is internally balanced and if not internally balanced it is weighted to work with the 6g72 There is reasons that the engineers who designed this engine did they things they did. Nobody has seen any positive experiences from using these said " Performance pulleys" .
I am currently using an underdrive pulley and it does no harm rides like a champ and shows significant gains!
 

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As long as the UD pulley is secured properly it shouldnt vibrate enough to throw any codes, in fact you should notice signifigant gains in performance :twothumb: Worse comes to worse you could always order a factory pulley from an oem website
 

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"Suck my unit"
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Discussion Starter #11
Ok so anyone with this, r u guys seeing any big gains?
You dont really gain anything. The engine just revs up slightly faster. It basically compliments other mods and if you have more mods it will be more noticeable.
 
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