External vs internal balance

[Rex T.]

Why are 454 and larger big blocks externally balanced rather than internally balanced? Also, how difficult is it to balance one internally and what about an internally balanced crank for a 454? Just curious. As always, thank in advance for your help.

Rex

[Duke W.]

Re: External vs internal balance

The longer stroke requires greater mass at the ends of the crankshaft to balance the first order rocking that's generated by the reciprocating mass.

Chevrolet deemed there was not enough space inside the crankcase for the added mass, so they chose to add it to the flywheel and damper.

I believe some aftermaket rotating/reciprocating assemblies may allow for internal balance in OE blocks for 4" and maybe longer strokes. Others may be able to offer some specifics.

Duke

[Joe L.]

Re: External vs internal balance

Why are 454 and larger big blocks externally balanced rather than internally balanced? Also, how difficult is it to balance one internally and what about an internally balanced crank for a 454? Just curious. As always, thank in advance for your help.

Rex

Rex-----

The reasons for external balance are as Duke described.

It's not too difficult to convert a crankshaft originally designed for external balance (e.g. Chevrolet 454, 400) to internal balance. However, it's expensive. It usually requires that slugs of mallory metal be added to certain crankshaft counterweights. For all practical purposes, I don't see any real reason to do this when one can just go with the external balance and counterweighted flywheels and balancers.

[Dick W.]

Re: External vs internal balance

It is possible and not too expensive to do by using mallory metal (which is expensive) I know of at least one Duntov with what was supposed to be a 427 actually had a 454 with internally balanced crank, but the correct flywheel and balance for a 427.

[Rex T.]

Re: External vs internal balance

Does anyone know anything about a big block crank called Kryptonite, made by LA Enterprises? Seems I remember hearing of them several years ago as being a premium crank for racing and hi perf applications. Just curous. I wonder if they are internally balanced.

[Clem Z.]

Re: External vs internal balance

Does anyone know anything about a big block crank called Kryptonite, made by LA Enterprises? Seems I remember hearing of them several years ago as being a premium crank for racing and hi perf applications. Just curous. I wonder if they are internally balanced.

just look for circular shaped pieces pressed into the face of the counterweights. some older balance jobs pressed the weights into the edges of the counterweights but this was a bad idea as centrifugal force could throw them out unless they were welded in.

[Dick W.]

Re: External vs internal balance

just look for circular shaped pieces pressed into the face of the counterweights. some older balance jobs pressed the weights into the edges of the counterweights but this was a bad idea as centrifugal force could throw them out unless they were welded in.

They will make a heck of a hole in the side of the pan if they come out!

[Clem Z.]

Re: External vs internal balance

They will make a heck of a hole in the side of the pan if they come out!

most balancers would weld a expansion plug in the hole to keep the weight in place since you can not weld tungsten except in a inert atmosphere. i have seen the pressed in ones come out.