I'm curious about balancing a stroker for an LT1. In ordering my crank from Callies, I was informed that LT1's are (I'll try to get the quote as close as possible since I don't have the actual email in front of me) "front internal, and rear external balanced. I'm assuming they were refering to the harmonic balancer as being internally, or "0" balanced, and the flywheel being externally, or counter weighted.

Is this correct? If so, why is it this way?

When I give the rotating assembly to my machine shop I'll give them my flywheel, and balancer. Should I make any special requests or include the whole clutch assembly (street twin)? I guess I just assumed that the LT1 was completely internally balanced, so the comments from Callies struck me as odd.

Can anyone shed some light on any of this?

Thanks,
Mike

 

They are correct, it started back in 86 (or 87?) when GM went to the one piece RMS. I have no idea why they changed it especally when older 350's were internally balanced front and rear. Maybe someone with more experience will come in and tell us...

If you're new motor is going to be internally balanced then I would give the machine shop the clutch assembly and tell them to neutral balance it as well. If you're going to stick with the stock balancing setup I would still give them the clutch so they can make sure the balancing weight is the right size for the rest of the motor.

My $02...

 

I just had an internal balance crank put in my engine. I just gave him my flywheel and he ground the weights on it down, didn't say anything about needing the clutch.

 

The reason that the 1 piece RMS crank is ext. balanced is because the flange for the flywheel on a 2 piece RMS is not round like the 1 piece. The flange is cast so that it provides the weight need to balance the crank. When they went to the 1 piece RMS, they had to make it so that the seal could slide over it, which cause them to lose this weight that was cast into the crank.

 

Mine was also Internally balanced..Make sure you get your flywheel neutrally balanced or your car will shake like crazy
Dont ask me how I know

Cody

 

Thanks for the replies so far.

So do most of you stroker owners go with with a neutral balance for the rotating assembly, and then have the clutch/flywheel neutral balanced also? Or are you using the stock style counter weighted flywheel, and the rotating assembly balanced with that setup taken into account?

I would guess having the assembly balanced to use the counter weighted flywheel would be beneficial, since there wouldn't be a need to balance a flywheel everytime it it replaced/changed etc..

Any input regarding this?

Thanks again,
Mike

 

texanmutt: Thanks for clearing that up.

That would only work if you were lucky enough such that the weight on the stock flywheel just happens to be what the stroker needs too. Since you're changing the crank, rods, and pistons that probably wont be the case so you'll need to have it rebalanced anyways.

 

Hmm, maybe I'm not explaining it well enough, or maybe I just don't understand the balancing process.

It has been my understanding that, a machine shop can balance the crank/rods/pistons to accomodate a counter weighted (not neutral) flywheel and/or harmonic balancer like a 400sbc used to be from the factory. The whole rotating assembly with flywheel, and harmonic balancer are still "balanced", but they must be used together to achieve the "balance". For instance, you wouldn't be able to use a neutral balanced flywheel with this type of setup because the rest of the assemlby is "externally" balanced.

Now, assuming my Mcleod steel billet flywheel is counter balanced just like the factory flywheel (it should be), I should be able to tell my machine shop to balance the crank/rods/pistons to use this flywheel, and the whole rotating assembly with flywheel, harmonic balancer etc., is still "balanced", but again, must be used together to achieve this "balance". If I am mistaken on any of this, somebody please clear me up on this topic.

But, this is really not my question. My question is, how is everyone else balancing their rotating assemblies? Completley neutral, or externally ballanced like the stock LT1 assembly?

My brain hurts now LOL....

Mike

 

I believe that internal balancing is best, it places less stress on the crank than external balancing.

Rich Krause