Thread: 6" vs 8" balancer SBC

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O.K., here's my take on it. Nobody has ever told me the reason there are so many different dampers for a small block Chevy, but I'm thinkin' the factory engineers know more than I do. I do know the reason for a damper and it makes sense to me that because there are different strokes and weights of reciprocating assemblies, it takes different dampers to dampen the harmonic oscillations created in the crank every time a cylinder fires. If it didn't matter, the Chevy engineers would only have made one application for all small block Chevies. Take a look at a damper used on a 3" stroke crank and then look at the damper fitted to a 3.750" stroke crank. Lots of difference. The longer stroke crank has a longer "arm" and I reckon it takes more damper to dampen the oscillations because the arm deflects from center farther and springs back farther. Like I said, this is just my own figurin', nobody has ever explained it to me. And by the way, the piece is a damper, not a balancer. It doesn't balance anything.

For you who don't know what happens, every time a cylinder fires, there is pressure placed on the rod journal. That pressure bends the material from the journal to the center of the crank. It will only bend so far, then it stops and begins springing back the other way. It springs back past center until it can't go any farther, then it springs back the other way, etc., etc. etc. These oscillations are called harmonics. It is the job of the harmonic damper to dampen these vibrations so as not to destroy the crank.

I can't remember if it was on this forum or another one that I was reading recently. This fellow was trying to find a good crank that wasn't cracked for his DeSoto hemi I think. He had found a number of them that were no good because they didn't use a damper at the factory and harmonics had cracked every one he found. He finally found a good crank and was asking about fitting a late model Dodge 340 damper to it.

If it were my crank, I'd research what the factory fitted it with and use that particular damper, pretty or not.

Look at this list of dampers from Damper Doctor for small block Chevies.....
http://www.damperdoctor.com/Merchant...egory_Code=CHE