harmonic balancer???

[slim]

My dad has a 70' ford pickup. It has a rebuilt 302 in it. After sitting  a while he goes to crank it up and the whole thing starts shaking like crazy... we drive it maby 200 ft. and pull over and take a look at the engine it seemed like the bolt was loose on the harmonic balancer turns out that the harmonic balancer its self was broken. so we get a new one and now every time your go to crank/ drive it the bolt from the harmonic balancer comes loose can anyone help? Thanks

[Chryco Psycho]

locktite or a tack weld