bad Babbitt Bearing or Valve Poor Quality Valve Job

[OldCoach]

I have a 1950 Ford Custom sedan with 239cu in flathead V8. For over two years I've been hearing a rattle sound from the engine. One mechanic tells me it's bad Babbitt bearing(s). Another mechanic says the rattle is due to a poor valve job sometime in the past. The car runs very well; no oil leak or loss of power. The rattle is not overly loud but noticeable. Wouldn't the car have "blown up" by now if I had bad Babbitt bearing(s)?