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View Full Version : UDP's Balancers and that ever long Debate...



Cross
10-17-2008, 10:04 PM
So I have been reading up once again on that ever non-ending debate of the Harmonic Balancer and its Rubber Dampener ring or running without. (As is possible with some UnderDrive Pulleys like the March Kit which suggests the use of the stock pulley after putting the UDP on your car)
I have been looking into it for years and on the little V6's I enjoy daily driving I have found the rings to always be rotted out and frankly they are not needed in my views. All 4 motors don't leak oil, have great compression still and now run UDP's that do not have the ring.
I also did not feel any gains *Shrugs* just another mod but then they are 2.5L V6's and really its just a "Dammit I wanna play with something" change.

As for my real toy.... I of course felt the same way but I decided before I went to far with it I would read up again and it seems the debate STILL has not gotten any further. One side refuses to run without it... the other shows no signs of problems not using it.

So I thought I would ask here and see the fun that ensues... at the very worst we can all have a few beers and enjoy what could be a funny thread with a few sig worthy replies.

My personal views:
For a piece that is spin balanced originally then also looking at the use of a flywheel... and the fact that the stock dampeners 7/10 have a rotted ring... are you really getting the effects of that stock setup you were meant too?
(Right now the motor I own came with a UDP and no stock pulley on after it. Along that same line I have a stocker that's in ok shape sitting useless here just because I collect parts... as always.)

Since I def do not see over 7000rpms with this motor I am not as concerned and to be honest the new toy I am play with megasquirt on that maybe in the next 2 months will be ready... will be seeing 9000rpm's but again its a little V6 and I am def considering the same UDP yet again. (Sorry off topic)

However I can see how it does not hurt to have it on however my take on UDP's was more then just reducing belt size but weight. Now this is where my information may be flawed because frankly it seems the argument gets stuck other places.

With the UDP to me the loss of unsprung weight is the gain to me, less rotational mass on the crank front is the same to me as less weight on the rear (aka lightened flywheel) so if you gain (Or if you pref it worded, gain the ability to spin up faster) from a lighter flywheel why not a lighter crank pulley? The Added effects of a shorter belt only seem to sweeten the deal of yet just another mod added to the list.

Now with all that said lets see those come out and tell me I am nuts etc etc. (Keep in mind the vehicle is not being driven I am awaiting a BMR Tq arm and then a trip to the exhaust shop to connect my new long tubes to the exhaust I have. I have been working on my swap into the Formula and many other things for about 3 months now just finishing up and getting ready to get her completely dyno tuned).

Now to go grab a beer and get ready to be blasted lol.


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Someone else brought up how they do not see how the belts can not act as part of that dampener for the vibrations. I have no answer and would like to see that added in if it does anything anyway.

He also posted this information: (1994Z28Lt1 on LS1Tech)
i posted in your other thread one of the common arguments stating why you need a harmonic balancer... and it makes sense to me the the idea behind it, dampening the torsional vibration from the crankshaft.

but does the belt perform some the the same duties? stretching slightly and then retracting slightly during these pulses to affectively dampen the torsional vibration? but is it affective enough?

my personal viewpoint is to leave the harmonic balancer on. I dont plan on getting underdrive pulleys for my car since the gains are really too small since the water pump is not driven by the belt anyway. Driving in a straight line, your power steering pump shouldn't be working very hard, and there will always be nearly same amount of drag from your alternator. Lets say it takes 40 amps to maintain your battery and operate all the accessories, whether your alternator is turning 4000 rpm or 5000 rpm it still has to produce that 40 amps, therefore it will need roughly the same amount turning force to do so, except i would rather produce that 40 amps at 5000 rpm since it will operate slightly cooler because the cooling fan will be moving more air.

For me it's not worth the risk to remove the dampener since somewhere along the way its been accepted enough that pretty much every engine that i can think of has been factory equipped with a dampener

just some food for thought perhaps we can get a good discussion going
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So who else wants to chime in before I finally start my car up after the long swap, build and play lol.

UDP = UnderDrive Pulley

Here this is the UnderDrive Pulley Type most commonly found online:
http://www.jegs.com/i/Aeromotive/027/21101/10002/-1
And this is a Harmonic Balancer not attached or setup for a Main Crank Pulley but meant to be an addition much like a companion to the above UDP:
http://www.jegs.com/i/JEGS/555/51606/10002/-1

Z28pr0jekt
10-17-2008, 11:06 PM
what the heck are you talking about

Cross
10-17-2008, 11:10 PM
Under Drive Pulleys, Weights, Harmonic Balancers and how Vibrations are handled.

enjoi355
10-18-2008, 01:38 AM
what the heck are you talking about

hahaha that was funny cause i was thinking the same thing

Cross
10-18-2008, 02:06 AM
Is that better?

Z28pr0jekt
10-18-2008, 11:03 AM
It's not so much the content, it's the lack of content, we don't know what car you are talking about, what engine, what make/kind if udp

Cross
10-18-2008, 11:45 AM
..... An LTx Motor (Hints the LT1-LT4 Section) and the Under Drive Pulleys that obviously do not have the Harmonic Balancers Built on. (If you need a brand name I know eBay have cheapo versions of the March Pulleys I believe they are called, if you need a link to that product I can provide it).

But honestly what does that matter? Under Drive Pulleys with out Harmonic Balancers built on and the debating on running with or without them. Pretty point blank. (And in the LTx Section, hell it could be an an RX7 Conversion for all that matters.)

My personal findings on the rubber in said stock harmonic balancers is above as well as my thoughts and the thoughts of another member.

Here this is the UnderDrive Pulley Type most commonly found online:
http://www.jegs.com/i/Aeromotive/027/21101/10002/-1
And this is a Harmonic Balancer not attached or setup for a Main Crank Pulley but meant to be an addition much like a companion to the above UDP:
http://www.jegs.com/i/JEGS/555/51606/10002/-1

Z28pr0jekt
10-18-2008, 12:53 PM
I ran my march pulley fine for over a year, only problem I had was it was a piggy back type pulley so it actually added weight to the rotating mass.. i also had charging issues because i didn't get the alternator pulley only the crank pulley

i ended up taking it off because of its severe uselessness

Cross
10-18-2008, 12:58 PM
Thats what I am talking about, running without the piggy back as you put it.

The Harmonic Balancers function is to handle Tors. Vibrations but between the belts and the fact that almost every stock Balancer I have seen the rubber ring is dry rotted is it really doing anything or is there any difference from running the car with just the UDP.

Z28pr0jekt
10-18-2008, 01:00 PM
Thats what I am talking about, running without the piggy back as you put it.

The Harmonic Balancers function is to handle Tors. Vibrations but between the belts and the fact that almost every stock Balancer I have seen the rubber ring is dry rotted is it really doing anything or is there any difference from running the car with just the UDP.


Ever see the pinks episode where the guys balancer falls off as he does his burnout?

He made one run without the balancer and the motor blew up.

I don't think its so much the rubber ring that makes the difference but the balanced weight of the balancer itself

If the motor is internally balanced and you get the UDP zero/neutral balanced I dont THINK there would be a problem running only the UDP

I hope im catching what you're asking, I just got back from the gym so I'm a little drained right now

Cross
10-18-2008, 01:02 PM
But from my understanding the LTx is externally balanced but at the Flywheel. So if this was a concern the lightening of the flywheel would cause this problem as well correct?

chevy42083
10-18-2008, 01:04 PM
Personally... I think the dampener is there for a reason... so IF I wanted some gain, I would run a smaller pulley/dampener combo. I think the march setup is a 1/2 azz way to do it. The UDP with dampener moves all the weight closer to the center line, which effectively makes it easier to spin, as well as under driving the accessories.

I wanted one, but went cheap with a stock replacement (I only have one acessory anyway... alt.... so it wasn't a big deal).

Cross
10-18-2008, 01:09 PM
So whats your feeling on the stock ones rubber being dry rotted often thus causing it not to do its job. Does it then become the same as just the UDP and how many cars do we think are out there with that problem?

Besides the belt idea or the flywheel weight change. I keep going over these things and for me personally to this point I have not found any evidence besides personal comfort that makes me lean one way or the other.

EGR, AIR, Cats, Stock Tuning, Stock Exhaust all has its purpose as do injectors, TB, the list goes on. We modify these all the time just like the coolant bypass mod.

Z28pr0jekt
10-18-2008, 01:09 PM
But from my understanding the LTx is externally balanced but at the Flywheel. So if this was a concern the lightening of the flywheel would cause this problem as well correct?

Yes it is external BUT

say for my new setup... internal balanced 355... so i have to get my flywheel and balancer/damper zero balanced..


Simply having a lighter flywheel will not cause a problem so long as it is still balanced within spec of the LT1
Like on my current stock balanced motor I have the spec billet steel flywheel which is much lighter than the cast iron stock flywheel but it is balanced to the LT1 from spec

Z28pr0jekt
10-18-2008, 01:10 PM
So whats your feeling on the stock ones rubber being dry rotted often thus causing it not to do its job. Does it then become the same as just the UDP and how many cars do we think are out there with that problem?

Besides the belt idea or the flywheel weight change. I keep going over these things and for me personally to this point I have not found any evidence besides personal comfort that makes me lean one way or the other.

EGR, AIR, Cats, Stock Tuning, Stock Exhaust all has its purpose as do injectors, TB, the list goes on. We modify these all the time just like the coolant bypass mod.

Can you show me a picture of this rubber ring, I'm not sure I've seen it before and don't want to respond on something I don't know about?

Cross
10-18-2008, 01:11 PM
Umm hold on let me find the extra one I have lol.

chevy42083
10-18-2008, 01:15 PM
I guess I've never seen a ring bad enough that I thought it would be a problem.
Then again... I've only seen a few.

Cross
10-18-2008, 01:19 PM
Ok this is the one I still have and its in ok shape but you can see the start of the rubber going south.
http://i62.photobucket.com/albums/h98/CrossGT6/SNC11267.jpg

The ring there is the rubber spot I was ref. too. I have seen them so bad that the Upper part just spun off the lower end and left a rubber mess and nothing else in sight.

Z28pr0jekt
10-18-2008, 01:22 PM
ha i never even noticed that rubber ring in there... i can't imagine they weigh much at all so i can't see that putting off the balance whether it's there or not... what is the purpose of the rubber ring?

Cross
10-18-2008, 01:24 PM
Thats the part that does most of the work absorbing said Tors. Vibrations.

Z28pr0jekt
10-18-2008, 01:27 PM
I call shenanigans on that.. idk.. I can't imagine my balancer has much left to that ring and my motor seems fine (for the most part haha)

i mean in the pics do you see a rubber ring on either of these? its hard to tell as they are all black

http://store.summitracing.com/egnsearch.asp?Ntt=ati+super+damper&N=700+4294908216+4294908395+4294840140+4294889104+ 4294908198+115+4294871838&Ntk=KeywordSearch

Cross
10-18-2008, 02:00 PM
Thats because on those from what I was reading that ring is inside on some of them or they may have a different design.

Remember many cars from Mazda, Ford, Chevy you name it have the same rubber ring setup. Its most likely cheaper but you tell me then;
How does a Metal Object absorb Tors. Vibration?

Z28pr0jekt
10-18-2008, 02:04 PM
I couldn't answer that as I'm certainly not any type of engineer haha.

But how does an 1/8inch thick deteriorating rubber ring absorb vibration? haha

Not trying to debate this so I think I'll just shush for now as I'm definitely not the most knowing here

Cross
10-18-2008, 02:07 PM
Actually you hit the nail on the head, thats what I have been asking for some time.

Here is some information about whats going on if that ring was working correctly:
Again a Copy and Paste from 1994Z28Lt1:
Otherwise known as vibration damper, harmonic balancer is a device attached to the vehicle’s crankshaft to minimize torsional vibration. As the cylinders fire, the crankshaft transports the power. The front section of the crankshaft suffers from the impact of the said power, due to this, it often moves before the rear part of the crankshaft. And this movement yields a twisting motion. Once the power leaves the front, the halfway twisted shaft unwinds and then snaps back in opposite direction. Even though it is small, the unwinding process gives torsional vibration.

To minimize this vibration, GMC harmonic balancer is employed. This vibration damper is made up of two pieces attached together by rubber plugs, spring loaded friction discs, or both. As the power coming from the cylinder gets to the front of the crankshaft, it attempts to twist the harmonic balancer’s heavy portion. But it usually ends up twisting the discs or the rubber joining the two damper parts. The front portion of the crank can’t turn the way the damper did because the force is being consumed in twisting the rubber and speeding up the damper wheel. And this causes the calm operation of the crankshaft.

GMC harmonic balancer doesn’t just act upon vibration. It also helps in extending the service life of the engine by reducing wear on the main bearings and journals. Plus, GMC harmonic balancer helps in preventing defects and failure on the crankshaft. It is great preventative maintenance for your GMC vehicle to replace damaged and defective GMC harmonic balancer. So if ever you notice that your original GMC harmonic balancer is already defective, have it replaced immediately
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