I bought the SFI fluid damper below at 440source and it has been tested...

http://store.440source.com/Fluid-damper-SFI-Certified-Black-New/productinfo/200-1024/

Most tractors I work on only rev to around 3000rpms, so you are a little higher then that. Most people learn the hard way if you are building a performance engine don't cheap out on parts. I have seen enough failures on offshore parts to either stick with good oem parts or pony up for the name brand stuff.

I'm 99% sure that's the model another board member had fail during dyno testing.

What damper is on the engine now? I suspect 6400 is way past what Chrysler would have expected for an OEM 440; Gen 2 426 Hemis had a different damper than an RB wedge.

it has been tested
Yes, it didn't blow up.
A solid hub would also pass.

Again: except for accepting the manufacturer's word, there is NO WAY to tell if the damper is tuned to work at the specific RPM points ("harmonic orders") that are sensitive in your engine. A typical V8 has several, at least one occurs below any RPM you would use constantly, and some way above your RPM limit. A V8 crank with 400 Hz frequency (way above L6, below V6) has orders at 24,000 RPM, 12,000, 8,000, 6,000, 4,800, 4,000, 3,429, 3,000, 2,667, 2,400, 2,182, etc. but not all are equally destructive.
There is a reason why all car manufacturers make a different damper for each engine. They also make some for different applications for the same engine: the Ford 289 4 bbl. 220 hp damper will not work on a 271 hp engine since the bigger cam needs damping above the 220's damper range.
What affects damper design? It's a long list and has nothing to do with power, compression ratio, rod geo, or balance factor.
The factors that determine the natural frequency of vibration include crankshaft length (number of cylinders in a row, number of main bearings), weight, and stiffness (rod and main journal diameters, stroke length, journal overlap). The Young’s Modulus of Elasticity (stiffness) of most steel material (forged, billet) is very similar so 4130, 4340, and mild steel are almost alike - but cast iron is different.

That's why they have SFI dampers for racing. It's not a good place to save money, imho.

An update to this: 440Source did offer to replace the balancer with a new one today. As I'm not excited about having the same issues and admittedly making more power than originally intended, I politely declined.

I do appreciate them getting back with me.

Couldnt send it back for “store credit”?

Good - they are more likely to give you credit than a refund.

So many of these aftermarket dampers fail after such little use it's ridiculous.
I've run stock old dampers on a few engines I raced and never had a problem.
The only one I had fail was a BHJ damper...it replaced a stock damper b/c I was worried about it, lol. BHJ repaired it, but refused to discuss the issue.

The car crosses the 1/4 mile stripe at under 5200 and is rev limited to 6400. Last Fall as a stopgap solution and so I could move the car in and out of the garage over Winter, I installed an OE balancer. It is most likely going to stay for a while.

I'd leave it on there too. It's 100% better than the cheap dampers out there...as you know.
ATI, Fluidamper, or Innovators West is all I'd use if going w/ a new one. Never used an IW piece, but heard they're good.

I was scrolling through this to see what you ended up replacing it with, as I sometimes worry about my stock one...

Looks like I'll stick with the 50 year old unit...

We can thank General Motors for this problem. They were the ones sending them into the grandstands hitting people

Buddy of mine blew one off a 289 Ford at Assumption. It made a hole in the track you could drop a golf ball in to, and a piece went through the wall of the concession stand and hit a lady in the butt.

Bob Glidden had a cast dampener on one of his Ford motors in 1980 explode on the starting line while testing and almost ruin the complete front end on his Fairmount Pro Stocker at the 1980 NHRA World Finals at Orange County raceway after he lost the sponsorship with Mopar when they went bankrupt the first time in 1980 .
That is the main reason NHRA started requiring SFI dampeners after that
I've had the outer ring come off of one of my old 1957 392 hemi motors while driving it, luckily the lower pulley and belts kept it on

What about the BHJ failed?

The aluminum hub ones I've seen fail crack one of the webs or fingers

I was working the starting line at Jackson County Sports Park at a NHRA points race. My buddy Warren was standing next to me. A Chevy Camaro modified car was doing a burnout and Warren fell over and the camaro went silent. The idiot had drilled holes in a stock dampner for a crank trigger. It exploded part of it was embedded in the concrete starting line and part of it took a chunk out of Warren's prosthetic leg. We were lucky that day.

I used to run the BHJ aluminum hub dampner on my stocker engines still have one in the shop. Never a problem.

So why did you raise such a fuss in public?