Sorry i couldn't embed the video but the link will take you there. This is a video and subsequent pictures of what happened when the flywheel let go on one of our customers new 557 ci., Kaase headed BOSS motor. The heads on this motor are the first production set that Kaase sold.
1st off, lets all thank God nobody was hurt. 2nd of all, maaan that sucks. Please, I don't want to even know what that engine costs and how much damage it caused. Nonetheless, it is a monster though. I can tell.
the bellhousing was sfi certified but the fly wheel was not. the only reason that the bellhousing didn't contain the flywheel when it let go was that the bolt holes in the block broke.
From the photos it looks like you used standard bolts to mount block plate and bellhousing. Im also curious if you did the same to mount flywheel. Did somebody forget to torque bolts.