Dampers are a great topic - I'm surprised there aren't more threads covering the physics of them!
First off, I'll just say I used this Powerbond damper on the 408 in the avatar. The pulleys all lined up in their stock location using it without issue.
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I had purchased an ATI and another one but sent them back due to their significantly higher weight. This one came in at something like 7-1/2#'s. (I think it was the ATI that was like almost 13#'s!)
So which one would be "better" or more correct? I dunno so I went with the lighter one. Here's why:
As part of normal OEM engine development, you instrument up a crank and run the engine throughout the speed and load ranges to see where the torsional vibrations "light up." Then you design a damper with the proper inertia ring mass and rubber durometer to dampen out those peaks and bring the overall vibrations to an acceptable level. If you have the wrong mass or tuned frequency, you can actually make the torsionals worse!
Since none of us on can do (or do) that development work, we're left choosing a damper from a myriad of them out there with wildly varying engineering properties and no knowledge as to what is needed. The only knowledge we really have is tribal knowledge or someone else's experience with a particular piece. So with no absolute knowledge of something better or worse, I chose to not add some big heavy one out there on the nose of the crank. (I also know this damper is used quite a bit by the guys at a local engine shop.) In the 3 years since this engine went into my car so far it has served me well. Note that I shift it right around 6200 rpm and it traps about the same running 11.1x's et's.
Just my .02 cents as a retired OEM engine engineer!
