bad vibration, possible balance issue. questions!

[1QUICKZ28]

If vibration has been there from day one I would definitely start by talking to the engine builder. Since he balanced everything. Did you try running it with the stock damper he used to balance everything? Is the engine internally balanced? If so, verify that he neutral balanced the flywheel. LT1's are neutral balanced in the front and externally balanced in the rear via the flexplate or flywheel from the factory. Aftermarket flexplates are balanced to match the factory stuff unless specified. I'm assuming he internally balanced the engine. Did your builder assume the flexplate was neutral balanced and not touch it? Did he do something to the stock damper to help balance the engine? Personally I would lean towards the flexplate since you're having that bad of a vibration. Since it's a 2pc balancer you could remove the damper part from the hub (leave hub portion bolted onto the crank) and start briefly to see if vibration changes.

Just sharing some thoughts. Let us know how you make out.


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[bufmatmuslepants]

You said "stock stroke crank", but is it a STOCK crank? Or an eagle cast crank? Wobbling damper and vibration has been seen alot when an eagle cast crank snaps at the front.