Reply to "Stroker engine vibration"

I agree with Marlin here.

Let me state it slightly different though. I think that it is best to tell the engine balancer person, DO NOT UNDER ANY CIRCUMSTANCES TOUCH THE BALANCE OF THE FLYWHEEL AND DAMPENER. IF YOU NEED TO, ADD MALLORY METAL TO THE CRANKSHAFT.

If you do not, they will balance the engine the easiest way for them, and that USUALLY means taking weight off of the flywheel and dampener.

If they do that, changing a flywheel or dampener will throw the reciprocating assembly into unbalance.

That is what it sounds like you have. Get the original flywheel back, any way you can. I'll bet that is the problem?

It is also a very good idea to balance the clutch as well, even a brand new one in the box.
I always have them done when I send an assembly out for balancing.

I had many engine builders tell me that you won't even see a "good" balancing job until over 7000rpm's.

I may be wrong here but if it is vibrating enough the dampener/balancer can fail on this.

In any case, best of luck with this situation.