Help with Timing, Vacuum and Backfire - 289c.i.

[67DownUnder]

Hi Agazzo,
How old is the harmonic balancer? It's the bit mounted on the front of the crank shaft and has the timing marks on it.
Basically it is a steel inner and a steel outer which are bonded together with rubber.
After 30 odd years the rubber perishes and the outer moves with respect to the inner. Timing marks are no longer valid.
Unbelievable difference when I replaced it on my 67.