Engine Balancing Basics - Need help

[Chevyguy]

Internal balancing is always a better route. The factory longer stroke motors used external balance since there was less room for the counterweights inside the engine. The heavy Mallory metal used to create a 0 balance motor is wayyy too expensive for any production motor. That said, a properly balanced external balance motor will work just fine (buliding an external balance 454)

In the case of the 302 50 oz balance, Ford wanted to reduce the static mass of the crank, this probably saved a few bucks, and some total vehicle weight. The 50 oz of weight makes 200# of force, but this is not mass, so the motor burns less gas etc....

As for why the shop did not want a stock balancer. The stock counterweights are probably prone to inaccurate weight or location, plus they are not as durable as a good aftermarket one.

You should always have the flywheel and balancer you plan to use when the motor is balanced to make sure everything is smooth. The shop will check the flywheel and balancer to make sure they have the correct counterweights, sometimes they will balance the motor with your balancer and flywheel as well.