Okay here is the story. I built this motor. I am using a Eagle stroker kit.
I ran into problems with the t56 flywheel not being neutral balanced, so I had that problem fixed. The engine needed new bearings because the bearings where shot (Only 500miles on engine). I got all the bearings replaced, Flywheel neutral balanced, put the car back together. Start the car, Runs very smooth, notice the balancer has a slight wobble. I bought a new keyed crank hub and a new jegs sfi balancer. It still does the same thing. Pulled the motor out today, took it apart, put a dial indicator on the nose of the crank, no movement, straight as can be. I put the both keyed hub on the crank and rotated it is off a couple of thousands .003, on the hub. I am going to take the whole RA including flywheel, keyed hub, and balancer to get rebalanced. Would balancing the whole RA fix this problem? The front balancer damper moves a lot when the engine is running. Could the crank be flexing? It is very noticeable at idle.

 

was there any other noise when the motor was running? You could have a cracked crank but I would suspect some noise...

 

no noise. engine runs very smooth.

 

Either the hub is bent from pulling it off or the balancer is machined wrong. i would take those two parts to the shop and ask them to check them before you do anything else

 

Is there any evidence of the crank moving forward and backward in the block? May have too much end play.

 

I tried 2 different hubs and 3 different balancers.

I have a stock, Professional Products, and a Jegs SFI balancer

 

End play is tight. I put new bearings in.

 

Wow, Sorry I reread your post and see that you tried a few different things. Wonder if it is shaking and you can't tell. Do the dampers have rubber in them? Or are they solid metal?

 

The Jegs SFI looks like it has rubber on it, the stocker and professional product damper have rubber. It is very weird. I am hoping it is just unbalanced. I dont want to pay for a new crank if its cracked.

 

Okay. After banging my head a couple of times I think I found the problem. I have a LT4 Extreme Duty timing chain on the engine, The crank sprocket is machined wrong. I took and measured the thickness of the sprocket and in some places it measures .208 and if you move around it i get a thickness of .220. I put a stock crank sprocket on the engine and reinstalled the hub and checked the runout and it was near perfect. The lt4 sprocket was causing the hub to bend a little bit.

 

As much as that thing costs to have runout like that, what a bunch of horse ****.

 

Send it back--Get another one--- Tell them to put that one where the sun don't shine.

 

I bought the timing chain last november

 

And you have had a problem ever since and just found it.
They would want to know.

 

No. It has been a long process of building this car. I only have 500 miles on it