Flex plates

BVoelzke said
Good point !!! but no this is a totally different engine combo . I think I might have found the problem : when I took the motor out the passenger side motor mount rubber was broken , when I last changed the oil during winter maintenance I found loose bell housing bolts on the same side . Although I have a torque strap on the drivers side I am thinking the broken motor mount is causing the engine to move around thus causing the bolts to come loose and cracking the flex plate . I am thinking I need solid motor mounts . BTW its an ATI Super Damper rebuilt by them 2 years ago and the motor was on the dyno ( thats how I know the hp. and tq. numbers ) before installation in the car

The engine was run on a dyno but not with the torque converter. Rubber mounts won't cause vibrations. But if the rotating assembly is out of balance everything will vibrate loose. .

Back in the 70's I had an old Harley with a stroker kit. It had a vibration that would sting your legs on the tank. The women loved it "Good Vibrations" but the bike didn't, parts just kept falling off the bike. The licence plates would crack off like lightning hit them.