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Old 05-24-2008, 09:13 AM
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steel or aluminum harmonic balancer?

Hi Guys, I have a 383ci sbc and the hub on my balancer cracked yesterday and I need to replace it. Is the aluminum balancer a better idea because of it's light weight or does it not make a dif??????????

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Old 05-24-2008, 10:17 AM
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Lighter is always better when it comes to rotating mass. Just make sure the damper you choose is appropriate for your combination and end use. I'll assume you're using an aftermarket crank (and not a factory 400 crank) and so it's neutrally balanced. I use an aluminum shelled ATI Super Damper on my 388 LT1. Very expensive (almost $400) but a very high quality part, so worth the expense to me.
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Old 05-24-2008, 10:42 AM
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Thanks for the reply Notorious, That is the damper I was considering. Ya not cheap but if it's good it's good. Done deal on Tues. My ride sits still over a great weather week end, damn I hate when that happens.
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Old 05-24-2008, 12:10 PM
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The purpose of the piece is to cancel vibratory harmonics that are set up in the crank by the power pulses each time a cylinder fires. An expensive aftermarket unit is not necessary if you are not planning to race full-time in a class that is structured by lbs per cubic inch and need the advantage of lighter reciprocating and rotating weight. I can think of better places to spend $400 in a street motor.

If the rotating assembly is internally balanced, use an 8" damper off a 350. If it's externally balanced, use an 8" damper off a 400.

8" 350. Uses 2:00 timing tab location.
http://www.damperdoctor.com/Merchant...egory_Code=CHE

8" 400.
http://www.damperdoctor.com/Merchant...egory_Code=CHE
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Old 05-24-2008, 12:32 PM
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I'll admit I have a lot of money in this engine, but it's not just a weekend toy. I drive it daily and sometimes race it both on closed courses and at the strip. The super-light damper is just one part of a highly efficient and reliable performance engine. Lightweight crank, rods and pistons (all forged), internal engine coatings, full roller, tight quench, etc. all combine to make a very strong performer that also gets phenomenal fuel mileage. On the highway, it's only 1.5 mpg off of what my stock, four cylinder Nissan Altima gets. And I think I can get it to 30 mpg before I'm done. (currently 28.5 mpg best @ 68 mph cruise) Not bad for 400 RWHP..... Every little thing helps, if this is one of the goals for a build.
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Old 05-24-2008, 01:05 PM
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I can see where the cost is justified in your case, particularly if you are going quicker than 11.00 at the strip and therefore are required to have an SFI 18.1 damper. I was just making the point that it would not necessarily be justified on a grocery-getter type street motor. Thanks for the details on your setup.
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Old 05-24-2008, 01:41 PM
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Quote:
Originally Posted by Notorious
Lighter is always better when it comes to rotating mass.
I disagree. It doesn't affect HP appreciably, and as anyone who has driven a manual-equipped car with too light a flywheel will tell you that its annoying as hell. Choosing the RIGHT weight for your application is what will work best. Aluminum itself (as a metal) will absorb some vibes on its own a little better than steel, but the whole point is to use inertia on a viscous or rubber ring to absorb torsional vibration. Without the intertia of the lighter aluminum it doesn't absorb torsional vibrations nearly as well. The bottom line is, you'll be saving 4 lbs on a rotating assembly that weighs nearly 100 lbs when you add in the torque converter or flywheel. Plus, all of its weight is in an 8" diameter which means its ligher weight has very little effect on a crankshaft with a 14" flywheel or 12" torque converter.

Aluminum race dampers are one of those things best left to racing in my opinion. Its one of those things where you potentially seriously compromise damping in order to chase that last split second advangage over your competition. On the street I guarantee you'll never know the difference except in your wallet.

Less is not better; correct is better.

Of course in his case it might help a half a tenth, but if that car sees any street duty, I'd keep the added torsional damping of the steel unit.

Last edited by curtis73; 05-24-2008 at 01:56 PM.
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Old 05-27-2008, 09:25 AM
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Sorry guys, that I couldn't get back to you sooner, had some family issues come up. I want to thank all of you for your input you have been extremely helpful. I will put the money in better places in the truck and buy a steel HB instead of aluminum. It definitely sees more street time than track time.

Thanks,
Apache 10
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