internal balancing

[timovilmi]

While thinking different options for my 408 stroker project I have found out that there are both internally and externally balanced kits for 360 block.
I know the difference, but which one is better?
From the factory 360 is externally balanced and if I do it internally, this means I have to remove weights from damper at least, but is there something else too?

[darren509]

Whoa!! If your throwing money for a stroker do yourself a favor and spend the extra money on an Fluidamper. Taking weight off the old one is an option, but have you ever seen an old one slip?? Youll be chasing your tail trying to figure it out.

[darren509]

One more thing, internally balanced engines make it easier to swap parts on and off: torque converter or flywheel and damper. Good luck, Im saving up for my own 408

[timovilmi]

OK, I see what you mean, but is internally balanced generally speaking stronger than externally balanced?
I just wonder why Chrysler ever decide to do it externally.
I have some experience with European cars and these are all internally balanced. Maybe externally is cheaper for the factory

[DartGT66]

Internally balanced engine is stronger and has less harmonics than an externally balanced engine. Don't think it really is a concern in a moderate engine, but switching converters and dampers is easier in an internally balanced engine. I would propably just get an externally balanced engine, or buy iot unbalanced & have it locally balanced externally with a B&M flexplate.

The reason for external balancing is, that there is not enough weight in the crank counterweights for internal balancing.

In a typical "straight" European engine this is no problem, the cranks are balanced in to zero weight and then the rod big & small ends + pistons are balanced separately, they do not affect the crank balance.

In a V8 engine the crank is balanced differently using "bobweight's" in the cranks rod journals. There are weights attached to the journals during the balancing of the amount of two rod lower end + bearings and one piston, pin+ ring and rod upper end weight / journal. To offset this mass the crank must have counterweights.

There is only room for a certain diameter counter weight to rotate in the block with the piston & rods, and you may not be able to get enough weight in to them to offset the bobweight. This is especially true in big stroke engines that move the bobweights further away from the crank centerline.

To balance this kind of a crank internally, you have to add weight to the crank counterweights. This is done by drilling large holes in to the counterweights and pressing heavier metal blanks (Tungsten) in to them. This method is pretty expensive and in a street engine I would not consider it necessary.

[timovilmi]

Thanks for advise.
Maybe BMW have made V engines also like sraight ones, I had 750 with V12 and still believe it was also internally balanced.
Anyway, I visited yesterday at Hughes engines website and found out that they offer internally balanced stroker crank kits and the price was not bad at all.
I just thought it may be more safe to do it internally and if I count together the not balanced crank plus needed balancing work it may be even more expensive that way.

[345Dart]

Timovilmi
The lighter the piston you get the less you will need to add to the crank to get it internally balanced. I would spend the money on good forged pistons (not cast) and less on balancing/weight.
CP Pistons in California make a ±535gm piston that will save a lot of counterweight in a 408.:

[Tim_K]

There are 3 types of engines that are naturally balanced. This means that you balance the crankshaft/flywheel/damper by itself with NO bobweights, then you make the piston / rod combos all weigh the same, and you're done.

They are the Straight 6, Horizontally Opposed 6, and 60 degree V-12. There may or may not be other engine types that I don't know of that are naturally balanced.

[timovilmi]

Thanks, it seems that I may need more basic knowledge about car engineering.

[6 packin]

Theres a good artical in the newest issuie of Mopar muscle magazin get it very good info.