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Old 09-30-2007, 02:47 PM   #1
ejh25
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Default Lightened Crankshaft Pulleys on Built Motors

I know this has been debated and vetted fully, but just out of curiosity, are people putting lightened pulleys on their built motors?

Thanks,
Eric
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Old 09-30-2007, 05:27 PM   #2
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Personally, I would not...

Removing the factory balancer and replacing it with just a pulley in not a wise choice in my opinion...

The factory balancer my not be the best choice on a built motor...
It is far better to have one on there, than not to have one at all...

Years ago, many circle track teams removed the balancers from engines and put hubs on them...

They did this for 2 reasons...
The factory balancers would come apart a high rpms..
And people thought it would help by lowering the rotating mass of the engine...

What they soon found out was that all it did was drastically shorten the life of the engine...

Crankshaft harmonics would just tear the engines apart, literally...

Crankshaft failures and oil system failures, all stemming from the crankshaft harmonics, jump started the aftermarket harmonic balancer business...

Just my 2 cents on the matter....
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Old 09-30-2007, 05:46 PM   #3
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Quote:
Originally Posted by shvrdavid View Post
Personally, I would not...

Removing the factory balancer and replacing it with just a pulley in not a wise choice in my opinion...

The factory balancer my not be the best choice on a built motor...
It is far better to have one on there, than not to have one at all...

Years ago, many circle track teams removed the balancers from engines and put hubs on them...

They did this for 2 reasons...
The factory balancers would come apart a high rpms..
And people thought it would help by lowering the rotating mass of the engine...

What they soon found out was that all it did was drastically shorten the life of the engine...

Crankshaft harmonics would just tear the engines apart, literally...

Crankshaft failures and oil system failures, all stemming from the crankshaft harmonics, jump started the aftermarket harmonic balancer business...

Just my 2 cents on the matter....
Thanks...I'm fully aware of the harmonic balancer debate...I'm really just looking for input from those who have built motors and have used lightened pulleys and what sort of gains they've seen. I don't want this to turn into a harmonic balancer debate (i'll make up my own mind on that).

Thanks,
Eric
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Old 10-01-2007, 12:58 PM   #4
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fully built cobb block

I have read and read about the harmonic balancer debate.
On a Honduh engine (I4) or other non opposing engine there is a DEFINATE "rocking" or unbalanced caused by the engine running...

But acording to everything I have read, there is no need for a harmonic balancer on a subaru boxer engine.... even the stock pulley has no signs of being any type of balancer or harmonic absorber at all.

I'm running COBB lightweight crank pulley. and lightweight PS and ALT pulleys too.


Curious to hear what others have to say....
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Old 10-01-2007, 01:49 PM   #5
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I kept my stocker on mine...
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Old 10-01-2007, 02:42 PM   #6
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Quote:
Originally Posted by IllNastyImpreza View Post
But acording to everything I have read, there is no need for a harmonic balancer on a subaru boxer engine.... even the stock pulley has no signs of being any type of balancer or harmonic absorber at all.
The stock pulley is a torsional vibration damper... that rubber layer isn't there just for looks.
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Old 10-01-2007, 08:45 PM   #7
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Quote:
Originally Posted by x99percent View Post
The stock pulley is a torsional vibration damper... that rubber layer isn't there just for looks.
Don't debate this here. Not the purpose of the thread...I'm looking for experiences that built motor owners have with the USE of a lightened pulley. As in what kind of gains have you noticed? What if anything else have you noticed after install?
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Old 10-02-2007, 10:31 AM   #8
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Quote:
Originally Posted by ejh25 View Post
Don't debate this here. Not the purpose of the thread...I'm looking for experiences that built motor owners have with the USE of a lightened pulley. As in what kind of gains have you noticed? What if anything else have you noticed after install?
I will let you know when i get her up and running..... hopefully next week.




Quote:
Originally Posted by x99percent View Post
The stock pulley is a torsional vibration damper... that rubber layer isn't there just for looks.
basicly everything I have heard says the exact opposite...

have you seen the crank pulleys from any other type of engine? the Honda pulleys have an OBVIOUS, and huge rubber dampener, same with other cars, thier pulleys are monstrous compared to ours...

Last edited by IllNastyImpreza; 10-02-2007 at 10:39 AM.
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Old 10-02-2007, 01:16 PM   #9
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Quote:
Originally Posted by ejh25 View Post
Don't debate this here. Not the purpose of the thread...I'm looking for experiences that built motor owners have with the USE of a lightened pulley. As in what kind of gains have you noticed? What if anything else have you noticed after install?
OK, then... to answer the question in the first post: No, I would not use an aftermarket pulley, because there isn't one available at this time that is a TVD.

Quote:
Originally Posted by IllNastyImpreza View Post
basicly everything I have heard says the exact opposite...
So the rubber layer *is* there just for looks?

PM me, so that we don't gunk up this thread. I'd honestly like to discuss this.
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Old 10-02-2007, 04:00 PM   #10
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ar fab i believe make a lighter pulley damper, some guy has one on iwsti.com, but i haven't seen anything on ar fab's website.
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Old 10-02-2007, 05:11 PM   #11
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Quote:
Originally Posted by IllNastyImpreza View Post
basicly everything I have heard says the exact opposite...

have you seen the crank pulleys from any other type of engine? the Honda pulleys have an OBVIOUS, and huge rubber dampener, same with other cars, thier pulleys are monstrous compared to ours...
There is a reason that there is a huge difference in the looks and size of the outer ring on a boxer harmonic balancer...
Boxer engines have for less harmonics to deal with because of the opposing cylinder setup...
But they still have harmonics...
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Old 10-02-2007, 05:14 PM   #12
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I wonder why COBB tuning would create a lightweight pulley WITHOUT one...if it could possibly hurt your engine ???
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Old 10-02-2007, 11:15 PM   #13
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technically there is a difference. but, there is more to gain than what would be lost, running a light weight pulley. a properly built motor is ballanced to much stricter standards. the perrin works on my 525awhp with out flaw. bacically you would die of old age before your built motor would suffer from the lack of that lump of sh.t put on originally to pacify your, " my motor feels funny" to the local dealer. with high hp, tough motor mounts and all the hoopla, who gives a poop! the only do not is the cheesey " power pulleys". good luck and just do it!!!!
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Old 10-02-2007, 11:37 PM   #14
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^ woot
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Old 10-03-2007, 08:19 PM   #15
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There seems to be some misconception about what a Harmonic Balancer actually does...
It has nothing to do with balance at all...
You can balance a motor perfectly, down to the smallest weight you can possibly measure, and it still has Harmonics....
Yes the Boxer design has less harmonics than other designs, but it still has them...

To those that use a lightweight pulley, thats great...
Its a personal choice...

There probably is an increase in power by using the lighter pulley...
The same can be said from any mod that lightens the rotating mass...

But there is a difference between making it lighter, and making it more prone to harmonics...
There is a thread on here somewhere that shows the actual harmonics of a boxer with the factory balancer...

Somewhere I saw another test that was done without a harmonic balancer, and the difference in the harmonic charts very obvious... Crankshaft deflection almost doubled...

Will the difference blow up your engine??? Probably not....
But it will fatigue metal over time...

The more you flex metal, the harder it becomes...
Harden it too much, and it gets brittle...

How many of you have ever seen the oil pump gear split into two pieces???

Have you ever notice that boxers eat rod bearings at high rpms????
Even with the proper oiling system, they eventually eat them...
And when you tear it down, 9 out of 10, the mains look fine???
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Old 10-05-2007, 11:48 PM   #16
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Default harmonic balancers

It's true that factory balancers are used for stock motors but not for comfort of the occupants. They are there to give the motor reliability. Subaru would not spend the money otherwise. Viscous dampers are better and more costly, thats the question you should be asking is where to get a better harmonic balancer. Power pulleys and solid pulleys are racing parts and if you're building a motor you will be tearing down at the end of a season use one. Harmonics are magically destructive if not delt with. It's your toy do what you want. I doubt any of Cobbs motors that fail can be traced back to a harmonics problem.

As to the rod bearings, you could look at it like this: When a v8 motor makes 450 hp it's using 8 rod bearings about the same size as the subaru bearings so there is twice as much load on the same bearing in a subaru as a v8 making the same horsepower.

In my opinion the less harmonics developed in a motor is a smoother reving motor that makes more reliable power. Also the harmonics will go through the oil pump on a subaru and that must cause problems. I spun a harmonic balancer off my sbc when I missed a gear and you might also do the same on a suby. Thats one reason why viscous balancers are popular on high performance motors, they also cover a broader range of rpms.

Good luck whatever your choice.
Charlie
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Old 10-06-2007, 09:51 AM   #17
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It is funny that you mention a fluid damper...

I have emailed Fluid Damper numerous times about producing on for the Subaru Boxer...

Hopefully the will make one sooner than later...

charliew is exactly right in the fact that a fluid damper is effective for a much broader rpm range than an elastomer type...
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Old 10-06-2007, 03:31 PM   #18
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everybody email them@ support@fluidampr.com and maybe we can get them to show some interest
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Old 10-06-2007, 04:53 PM   #19
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Thats a good idea... If enough people show interest, they will make one...

The make other import ones... Just not one for the Subaru's yet...
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Old 10-06-2007, 05:24 PM   #20
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Here is my 9" crank pulley. Custom obviously. And never a problem.

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Old 10-06-2007, 05:35 PM   #21
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Quote:
Originally Posted by reddevil View Post
Here is my 9" crank pulley. Custom obviously. And never a problem.
Thanks. This is exactly what the post was intended to do.
What is the OEM diameter? Does it differ with the GC?
Thanks,
Eric
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Old 10-06-2007, 08:59 PM   #22
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OEM is 5.25". And the reason this one is so big is the supercharger it drives.
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Old 10-08-2007, 02:06 PM   #23
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Not a fan of fluidampr, but ATI DOES make one, they just don't sell it (openly).
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Old 10-22-2007, 10:07 AM   #24
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Default fluidampner

I have only fluidampner on all of my sbc chevys. They seem to be great and I would buy more than two for my subarus.
Charliew
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Old 10-22-2007, 10:22 AM   #25
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Talk to howard at AR Fab, they developed one with someone, not exactly sure who it was, but it is a bit lighter than stock but also a better than stock dampner. I have one that will be going on my built block that will be revving as high as 9k.
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