Externally balanced is when you bolt the flywheel and balancer and balance as a unit. You would remove weight from the crank and add to the flywheel. Must use the same balancer and flywheel with the assembly. External examples 400 SB and 454's. Most drag 454's are internally balanced anyway. Internal balance add and subtract weight from crank and rods. I think the Boss 302 Ford is external balance.
