What can cause so much vibration? I know the usual loose bolts and such or something broken internal. But I have no loose bolts and don't hear or find anyting internal to be broken. When I had the ignition cover off checking the flywheel I also checked to see if there was any play in the crank bearings, there wasn't. I checked the balance shaft as well, it was nice and tight and moved freely when the engine turns over. No metal shavings were in there, but then again I have a magnetic drain plug that I haven't checked yet.