lugnut wrote:
> You should be setting the timing with the vacuum line(s)
> disconnected and plugged. IIRC, yous may have a dual
> diaphragm advancer which I would lose if it is not a
> concours resto. If the timing is off that far with the
> lines disconnected, I would suspect that the outer ring of
> the damper has slipped, the damper is wrong for the engine
> or you have the wrong pointer installed. Also, make sure
> you are setting the timing from the #1 plug. On a Ford this
> is the front passenger side. I suspect you know this but
> some from the SBC camp do not. The cam you have is fairly
> mild and usually gives a decent idle.
>
> Lugnut

Damper would be my guess also seen it happen a few times on 302s.