Harmonic Balancer Failure

[zimmstoy]

Hey everyone,

I ran the 87 Camper Special 454 truck today had it cruisin pretty fast. Came home and parked it, shut her down and heard a horrible noise. Sounded like the flywheel broke in half. After further inspection i found that the weighted part of the harmonic balancer (the piece with the timing mark) actually separated from the balancer. It is rattling around pretty bad. Needless to say I need to replace it. Has anyone had this happen before? Is it as simple as a separated balancer from the weight or is there something deeper I should be looking into?

I was running the truck today around 85mph with the turbo 400 in there I suspect I was going around 4500-5000 rpm (is this a bit much for a stock balancer? Anything I need to look for in a replacement balancer?