i bought this crank from summit and in the magazine it says external balance and online it says internal balance. i looked on the manufaturer site and i came up with this.....

103523480 3.480" 350 int./ext. 1870 cast steel Internal balance in front, external in rear 192.00

its a eagle brand cast steel crankshaft. so which is it? and what does it mean?

 

I think you mis-read something.

That's a 350 crank. Stock 350 stroke. Doesn't need external balance at all. Doesn't say anything at all about external or internal balance.

The one right below it is a 383 crank. It describes itself the exact opposite of what you said. It is external balance on the front (400 damper required) and stock 1-piece balance on the rear.

The part # you posted is an all internal balance crank... except that it uses the stock flywheel, which is of course slightly unblanaced; although the motor is still considered internally balanced, in spite of having a small portion of counterweight on the dry side of the rear main seal.

 

It means you use a neutrally balanced damper on the nose and a bat-wing weighted flexplate on the rear. Read: Stock 350 stuff.

It is technically correct, but not what is conventionally meant.

 

where do you see it is internal? eaglerod.com is where i saw the internal frnt and external rear. does it need balancing?

 

The part # you posted is a 350 crank. It uses the stock 305/350 parts, with stock 305/350 balance. That means it's internally balanced, except that the last little bit of the rearmost counterweight, which should be located just to the rear of the rear journal (which, as close as is practical, is on the crank flange in the 2-piece motors), can't be on the crank itself because the seal has to slip over it, and so it's located on the flywheel. But since the crank is still dynamically balanced (i.e. the counterweights are split half-and-half on each side of the journal they counterbalance), it's internally balanced.

Internal/external balance refers to something other than whether the counterweight is on the dry side or the wet side of the seal. It refers to something different even from whether the crank contains enough metal to counterbalance the bob weight on its journals.

It refers to whether the counterweights for front and rear journals are equally split on the 2 sides of the journal.

But forget all that. Think STOCK. Don't bother with all this internal/external crap, if you don't understand it, it'll just confuse you. Put all that out of your mind. STOCK. That's the magic word here.

Yes it needs balancing; Eagle has absolutely no way to know what pistons and rods you'll be using it with, and so, cannot adjust the counterweights to exactly match YOUR other parts. So, like ALL other cranks, you have to get it balanced. In your case, this means, to the STOCK 305/350 spec.

 

From what you originally posted and from which I quoted: "...cast steel Internal balance in front, ..."

 

ok i called summit and they said to have it balanced with the factory flywheel. thats what i will do. thanks for the help

 

Ok, I sent my engine (L98) to the machine shop to have it balanced and they called me saying that it has a weight on the flexplate but the damper was for an internally balanced engine? Can somebody please help me? I don't know if I need to find a new flexplate or a new damper. I don't understand. What should be done to get this engine balanced??? It's an L98 with LT1 pistons and rods.

 

They should be able to balance it with your stock flexplate and your stock balancer. That crank is a stock replacement for your motor.

 

having it balanced with your dampner and flywheel sure leaves you a lot less options if you break a part or want to replace either of them