There are two ways to do a engine balance job. The shop can do either an "internal" or "external" balance job. The preferred method is to have the engine's rotating assembly (crank/rods/pistons/rings) "internally-balanced". That way the flywheel/flexplate & dampener are not needed & should not have an effect on the balance work. This is assuming you will be using typical aftermarket parts which should be of "zero-balance". OEM flywheels/flexplates & dampeners are not zero-balanced. However, if an engine is "externally-balanced", as most stock motors are, then the flywheel/flexplate & dampener become an extension of the balance work and you must have the correct "balance" in your flywheel/flexplate and dampener for ensuring the balance of the engine isn't mis-matched. If you ever need to change the dampener or flywheel/flexplate during the life of the engine, then it must be of the same "balance" as when first balanced. This is an advantage of building a cruiser motor (not putting your engine over 6K rpms) because you'll likely use the OEM flywheel/flexplate and dampener and can switch them out for another same balance piece if necessary.

So, since you're looking to build a Street/Strip engine, ask your shop to perform an internal balance job for you. However, by providing the shop with your new dampener, flywheel/flexplate would allow them to correct for any error in the new pieces, if they were off a little. So, for the above stated reasons, you for sure don't want to balance your engine using your old dampener (which probably isn't of zero balance), then buy and install a the new one (which probably IS of zero balance), because if you did that, that whole works would be out of balance big time!

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Originally posted by Ryan Wilke:
Mr. X:

Lastly, it's been said that the fluid-style dampener doesn't have as much 'RPM range' as an elastomer-style dampener. So for a street/strip ride that will see some higher rpms (over 6K) at times, don't try to make the 25+ years-old dampener stay together - I'd spend the $$ and go with an elastomer-style dampener, like the ATI unit.

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Actually, it's the elastomer type dampeners that have a narrow rpm range. Stock dampeners are elastomer type. These are relatively inexpensive to produce, and can be made fairly lightweight. The Fluidampr is a little heavier and more expensive, but works over the complete rpm range of the engine. It works very well at dampening torsional harmonic vibrations. I've used one on the mustang for 8 years with a stock crank and rods... running deep in the 10's at around 130 on nitrous. I've had zero crank related problems. The main things that turn people away from the Fluidampr is weight and price. It's a little heavier, but it works.

Good Luck!

I ran tons of nitrous through the FE's and used to have alot of trouble with the mains moving around. When I started running a Fluidampr it helped my main cap problem alot....didn't cure it, but it got much better.

I've read alot of stuff that bashes Fluidampr....I've never run an ATI or anything else, but I've been happy with Fluidampr so far and have never experienced any problems whatsoever....in fact, the first time I ran my FE motor with one on it I could feel a difference while driving the car, it smoothed out the whole ride. I thought I was nuts, but when I got back to the pits, Larry told me he could hear that it was happier....maybe we're both nuts...LOL.

A note on balancing....Do not balance your assembly with the Fluidampr on the crank. It has a ring that is suspended in fluid and will not repeat on a balancing machine. They are zero balanced so you can balance the assembly without a damper and then run it. An external balance application, like a 5.0, has a counterweighted hub that the ring bolts to....in this case, you would balance the hub on the assembly without the ring.

I'm not against running a different brand of damper, I just don't like to mess with a good thing when I find something that works for me. I've read claims that one makes more power than the others, but I've never seen these claims from an unbiased source....until I see something from a neutral source, I'll stick with what I know works for me.