balancing a 440

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69413valiant

69413valiant

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Building a 1967 440 for my valiant. Should i internally or Externally balance the motor and why. This is my first motor rebuild since I normally go low buck and use used motors
 
Cast iron is externally balanced Steel crank is stronger and internally ballanced . Steel is stronger but weights more. And if you have or ever plan in manual trans then I would do steel it works with both.
 
As a '67 it will have a forged steel crank and was intrenally balanced from the factory. IMO - I don;t build any engine without internally balancing it. Doing it this way is usually more expensive - sometimes 50% more than a similar external. But - we're talking maybe another couple hundred. For that money spent you get longer parts life and more longevity, more power and efficiency at any rpm level, a smoothness that you can feel, and the ability to swap bolt ons like balancers and flywheel/torque convertors with any nuetral units. The factory started externally balancing because the crankshaft counterweights became too light when the crank material was lowered to cast steel.
 
I have read that a cast crank 440 doesn't have enough weight in the counterbalances to balance internally. Is this an old wives tale or Internet myth? I just sent my 78 off to be balanced wnd had them order a harmonic damper and flex plate for it they used a weighted dqamper and flex plate and balanced everything with those pieces. I assumed this was proof of the story. Maybe the machine shop didn't know any better?

More info, reused reconditioned stock ly rods and KB hypers.
 
As mentioned, all cast cranks are externally balanced. Forged cranks are internally balanced - with the exception of '72-'73 440 6-pack which used a forged crank and external balancing to compensate for the heavier rods.

Externally balanced cranks can be "converted" to be internally balanced by adding heavy Mallory metal - but that can get spendy.

Always a good idea to have the rotating assembly balanced - and should be considered a must when replacing pistons, rods, or mixing parts from various sources. Every gram of imbalance equates to about 1 lb of force slinging around at 2000 rpm and that number climbs as the rpm's do.
 
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