External engine balance - how's it done?

I'm no guru on this subject but I'll share what I know. The process is the same for internally or externally balancing. The only difference is an externally balanced engine has weight added to the balancer and flywheel/torque converter 180 degrees opposite each other to balance the engine because the crank doesn't weigh enough to balance it internally.

BTW: This added weight out on the end of the crank opposite each other adds stress to the crank so that's why an internally balanced engine is better. You can internally balance any crank but that involves adding Mallory metal (very heavy metal) in various places on the crank and Mallory metal is very expensive.

To balance an engine they weigh the pistons then the heavy ones get material removed to match the weight of the lightest piston. Same goes for the rods. Then they figure up the bob weight (sorry, don't know that formula) and add the bob weights to the rod journals and spin it and remove weight where needed to balance it out.