454 Internal Balance?

Can any one in simple terms, tell me what makes a 454 internal balanced or External Balanced. Second question how big of a damper ( harmonic Balance) should I run. The engine I am planning will be blown. At the present I am researching this total project so I don't just throw money at it.

Thanks Art
:confused: :whacked:

The stock motor is "Externally balanced" it was cheaper for GM to add the counterweighting to the flywheel and balancer. The counterwieghts on the crank were already about max size for the block design.

This same motor can be "internally balanced" by using neutral flywheel and balancer. Then add "heavy metal" to the counterweights. Expensive. But the aded weight is more centrally located and reportedly is easier in the main bearings.