Underdrive pulleys, which one - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

veil_side_ · 07-27-2002, 09:22 PM

Okay I'm hearing many different things about Underdrive pulleys.  From my understanding there are some harmonics that are harmful to the engine, esp. the crankshaft, that are created when using some underdrive pulleys.  The stock pulleys bring a harmonic balancer that dampen them but many of the aftermarket pulleys don't bring this.  My question is which ones have them.  I hear this mod is worth it but I don't want to kill my engine.  Is the damage that bad?

wherezmytofu · 07-27-2002, 11:31 PM

yup u heard correctly...any kit gives u the extra pully that replaces the harmonic balancer is bad..thats why normally unorithox comes with 3 pullies and aem comes with only two...all u got 2 do it toss the extra pully <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt='

'>.....also...it is the same problem with getting to little mass...that was one problem with aluminum flywheels....with less mass they also have less dampaning power and can cause engine problems.......damn HARMONIC RESONESE!

veil_side_ · 07-27-2002, 11:54 PM

ah, so any kit that brings a third pulley should be avoided.  I heard bad stuff about Unorthodox Racing Pulleys but everyone loves the mod alot.

mazdog240 · 07-28-2002, 12:09 PM

you just don't want to replace your stock harmonic balancer (ie crank pulley).
I recently bought the Trust/GReddy kit for the Sr20 it came with three pulleys (water pump, alternator, and power steering).  So you want three pulleys, you just don't want to change the crank pulley.

wa-fu · 07-28-2002, 11:24 PM

Any aftermarket crank pulley you buy for the KA will not have a harmonic balancer.  If you call up Unorthodox racing and talk to them, they will tell you that a stock KA pulley does not have a "harmonic balancer" anyhow.
I have a Unorthodox pulley that has been sitting in my closet for 6 months.  Does anyone have any DEFINITE evidence that this mod will  cause engine damage?  Most of what I have read is just hearsay.  What about the "lightened flwheels cause engine damage" thing.

07-27-2002, 09:22 PM	#1
veil_side_ Leaky Injector Join Date: Apr 2002 Location: Arlington TX Posts: 56 Trader Rating: (0) Feedback Score: 0 reviews	Okay I'm hearing many different things about Underdrive pulleys.  From my understanding there are some harmonics that are harmful to the engine, esp. the crankshaft, that are created when using some underdrive pulleys.  The stock pulleys bring a harmonic balancer that dampen them but many of the aftermarket pulleys don't bring this.  My question is which ones have them.  I hear this mod is worth it but I don't want to kill my engine.  Is the damage that bad? __________________ VeilSide? i've never bought anything from them and never will!

07-27-2002, 11:31 PM	#2
wherezmytofu BANNED Join Date: Nov 2001 Posts: 1,873 Trader Rating: (0) Feedback Score: 0 reviews	yup u heard correctly...any kit gives u the extra pully that replaces the harmonic balancer is bad..thats why normally unorithox comes with 3 pullies and aem comes with only two...all u got 2 do it toss the extra pully <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/biggrin.gif" border="0" valign="absmiddle" alt=''>.....also...it is the same problem with getting to little mass...that was one problem with aluminum flywheels....with less mass they also have less dampaning power and can cause engine problems.......damn HARMONIC RESONESE!

07-27-2002, 11:54 PM	#3
veil_side_ Leaky Injector Join Date: Apr 2002 Location: Arlington TX Posts: 56 Trader Rating: (0) Feedback Score: 0 reviews	ah, so any kit that brings a third pulley should be avoided.  I heard bad stuff about Unorthodox Racing Pulleys but everyone loves the mod alot. __________________ VeilSide? i've never bought anything from them and never will!

07-28-2002, 11:24 PM	#5
wa-fu Leaky Injector Join Date: Mar 2002 Location: South Carolina Posts: 109 Trader Rating: (0) Feedback Score: 0 reviews	Any aftermarket crank pulley you buy for the KA will not have a harmonic balancer.  If you call up Unorthodox racing and talk to them, they will tell you that a stock KA pulley does not have a "harmonic balancer" anyhow. I have a Unorthodox pulley that has been sitting in my closet for 6 months.  Does anyone have any DEFINITE evidence that this mod will  cause engine damage?  Most of what I have read is just hearsay.  What about the "lightened flwheels cause engine damage" thing. __________________ ...got to find the reason why my money's all gone...

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07-28-2002, 12:09 PM	#4
mazdog240 Leaky Injector Join Date: Jun 2002 Posts: 88 Trader Rating: (0) Feedback Score: 0 reviews	you just don't want to replace your stock harmonic balancer (ie crank pulley). I recently bought the Trust/GReddy kit for the Sr20 it came with three pulleys (water pump, alternator, and power steering).  So you want three pulleys, you just don't want to change the crank pulley.