Internal/external balancing- I never have understood this

[priderocks]

Can someone explain internal and external balancing to me, and what engines it applied to?

[Changin Gears]

An external balance motor does not have enough mass in the counter weights of the crankshaft to offset the wieght of the pistons/pins/rods.  The external part is an offset balanced flywheel/torque converter and harmonic balancer.

This usually happens with cast crank engines (cast not as heavy as forged) or stroker engines (rods attached to the crank farther out).

Chrysler external balanced engines include 360's and cast crank 340's, 400's and 440's.  The cast crank 318's have a small piston diameter and short stroke so the mass of the counter weights is enough.

[moper]

What he said. External basically means using some form of counterbalancing weight outside the main bearing support of the block. What that does is get somewhat of a fix for the imbalances of the running engine. But because the weight it outside the mains, it tends to make the crank have to flex more just to do it's job. That uses power and can cause a crank to fail. The best way to get the longest life and most power is to internally balance the assembly because the countering weight is more directly opposed to the imbalance. You can internally balance cast cranks, but you spend more because the crank needs to have heavy metal, called Mallory metal, to the crank and it's expensive and more labor.