Harmonic balancer bolt

[Shady Rascal]

Peter S is correct. The SBC didn't use a bolt for a lot of years. Even my 74 model six cylinder doesn't have a bolt from the factory. Harmonic balancers fit snugly. If you're not spinning one up to a lot of revs, it's not likely to migrate off.

Why not keep an eye on it ? Every time you fill it with gas just pop the hood and shine a flashlight down there to make sure it's not migrating outwards. My money says if you let sleeping dogs lie that it won't ever be a problem. It hasn't been so far has it ?