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Author Topic:   Balancer vs. damper
Racer0
Dirt Full Roller

Total posts: 64
posted May 09, 2002 10:09 AM
Talking to the machine shop about balancing my rotating assembly they told me to get a good fluid damper. I then talked to other guys at the track who said not to run one cause they aren't made for the RPM's and could break the crank. They went on to say a stock harmonic balancer works just fine. Not sure who to believe. I see summit has an ATI "super damper" is this the same as a fluid or not? I don't want to waste money on something I don't really need. Guess I should add, the motor is a 383 sbc, hoping to turn 6000-6400 rpm. Thanks for any input.

c21
Dirt Freak

Total posts: 346
posted May 09, 2002 11:57 AM
ATI is the best, it is a high quality elastemer (sp) type, like a stock unit. Fluid types are OK (once thought of as "theway to go"), and are less application specific (dampens a wider range of frequencies).

If you want to drop $300, buy the ATI (my first choice) it is rebuildable.

Otherwise I would probably get a stock type or use a fluid unit if it were laying around (ie free).

I have heard of concern about the liquid inside the fluid dampers (dampeners)solidifying in some extreme cases (rendering them useless), but this could be BS.

Good Luck
c21

Monster
Dirt Maniac

Total posts: 135
posted May 09, 2002 04:58 PM
I'll put my .02 in here. I ran across a test that someone conducted(don't remember who, but they were credible).They tested 3 dampeners, and measured crankshaft deflection per firing impulse over time. The makes of the dampeners were not mentioned, but the type was, and so I was able to deduce whose dampeners they were talking about.Several dampener companies have used the results of this test to tout their own benefits. The 3 were ATI, Fluiddamper, and the TCI Rattler.The ATI was best at high rpm(over 6500), and as the rpm climbed, the advantage grew. The Fluiddamper was best under 6500 by a large margin, and the Rattler was in the middle(better than ATI down low, better than FD up high). An elastomer dampener(like stock) can tune out vibration very well, in a relatively narrow rpm band (hence ATI's available tuning parts). This means that any time you change bobweight by using lighter components, changing stroke, operating rpm,etc, you start moving out of the damping envelope of a stock dampener.A viscous type(Fluiddamper), by the nature of the shearing action of the silicone medium, has a very wide band of resonance. As a general rule, the larger the mass of the dampener, the better it will work,at the expense of engine response. The ATI is very popular in WC because of the fact that it can be tuned, and they have the means to do so. I use both, and have broken a $2000 reworked stock chevy crank with an ATI, and have also seen a Fluiddamper unbolt itself from the snout of a 7500+ rpm Ford drag race engine(4" stroke). I'm currently in the Fluiddamper camp, cause my personal engines are restricted and only turn 6500 or so. The ATI is degreed all around, which is kinda neat. IMHO, the best thing to do with the stock piece is to use it to prop your door open. Guys that can't afford a part always say that the cheap stuff is 'Good enough'. I love hearing competitors say that, but wanna puke when any of my guys say it! A good dampener, properly installed, will last until you decide to get rid of it.

sdhnc29
Dirt Freak

Total posts: 467
posted May 10, 2002 12:02 AM
Glad to hear you hate junk too monster !! We have used both the Fluidamper and the ATI over the years . Currently we use the ATI 7.250" on our unlimited , and our limited late model engines . I could never sell short the Fluidamper though ! I had one on our house car for over 3 years , same crank , same damper , and was still able to sell the rotating assembly when I was done with it .

------------------
Hendren Racing Engines
Rutherfordton , NC
(828)286-0780

c21
Dirt Freak

Total posts: 346
posted May 13, 2002 12:15 PM
Thanks for your .02 Monster, I love the education available here.

On the topic of balacers ... David Vizard has a very interesting article in the latest "Speedway Illustrated" comparing a few balancers in various sizes with the focus of the article being .... debunking the benifit of running without. Good stuff.
c21

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