I am using a 400sbc with a stock balancer right now. I went on summit racings website and picked my motor then externally balanced. After that it says to pick a neutral balance or 26oz imbalance and I have no clue which one. The flexplate has the weight on it so do I use the neutral one or do I use the 26oz one to make the extarnal balance on both sides? I have no clue what to pick.

 

Does your stock balancer have a weight on the inside ring? looking from the back of the balancer.

 

I dont think so. It's got the chunk "missing" of the inertia ring though. I dont think it has any weights inside it.

 

Is the crankshaft in the engine internal or externally balanced?

 

Externally balanced

Like I said before, once I selected externally balanced it led to to picking a neutral balance one or a 26oz imbalance one. Either one could work but only one is right and I cant figure it out.

 

An externally balanced crankshaft can't use a neutrally balanced damper and flexplate/flywheel.

If you use a neutrally balanced damper, the engine will have a terrible vibration and will eventually destroy itself. Buy a damper for an externally balanced 400/383

 

I know it will but summit offers those both for a externally balanced motor

 

Then you better call Summit and ask them. My guess is that if you choose a neutrally balanced damper, you'll get an internally balanced crank.

 

if your engine is a factory balance then it will use the 28oz weight. if the rotating assembly was balanced by you or a machine shop, then it could go either way depending on the crank and who balanced it.

 

Machine shop balance has nothing to do with internal or externally balanced. A machine shop can't take an externally balanced crank and make it internally balanced.

 

I was just thinking that when I read it but kept my mouth shut since I'm not a pro. I think I need the 26oz imbalance one. I just put a stock one on with timing tape and I'll deal with it for now.

 

True but aftermarket cranks can go either way. Thats what I was suggesting.