static balancing enough?

[FullNelson]

Well right now my motor is off at my machinist, and the bottom end is being dynamicly balanced to IIRC .5 gram among other things. If i choose to change my rods to somehting like Crower or Pauter, somthing that is statically perfectly balanced, would this throw off the dynamic balance?

 

[figgie]

and how would you know that they are infact "zero balanced". You take thier word for it?

Regardless, they still need to be balanced as a system.

 

[jdub]

Pauter rod weight is pretty consistent, but those weights (and pistons too) need to be factored in when balancing the crank. So does the dampner and the fly wheel/flex plate.

 

[Poodles]

Thought the dampener and flywheel/clutch doesn't matter as long as their zero balanced seperately as our engines aren't externally balanced?

 

[jdub]

It "shouldn't", but "should" is right between "F" and "U" in the alphabet

I always do it...call me anal. It doesn't cost anything and it balances the entire rotating assembly.

 

[Poodles]

But if you have to replace either component the balancing is now screwed...

 

[jdub]

Well, if the damper and flywheel or flex plate is already zero balanced (as they should be), it doesn't really matter. But, you are correct..you do not have to have these components attached. When I had mine done, I had the ATI damper and flex plate attached...I'm not expecting a failure of either...I wanted the rotating assembly to be as close as possible. The crank was also checked without these and was in spec. My CP pistons and Pauter rods all weigh within 1/10 gram of each other.

Balancing a crank is always a compromise...the dynamic forces acting on a crank include both reciprocating and rotating weight. Rod to stroke length ratio, piston ring drag, RPM, engine power output, etc all have an effect.