Erratic Timing
Thanks! That seems pretty clear. I'll have to look more into what curve is right for my engine, but I'm not spending much time past 4k anyway, so it doesn't make much sense to keep a spring that won't really do anything.
Like AJ and 273 said, you have to measure and plot out what is in there before making changes.
A stock 318 is relatively efficient at low rpm, and doesn't need as much advance at idle and low rpm as something more radical.
However, at least the early years of the 318, the timing should increase with rpm until at least 4000 rpm. That's a 2 bbl stock cam and compression - not hot rod.
As anti-smog requirements got tighter late 60s early 70s, the initial timing was reduced and longer quicker initial advances were used to get the timing back were it needed to be off-idle.
Getting above 3000 rpm with an electronic ignition, the heavy spring and longer advance was sometimes used to offset the time lost by electronic switching.
I'd set the initial timing at whatever it needs to be for your car. Then go from there. Setting it at 2600 to 3000 is for hot rod and racing setups.
If its not stable at the idle speed, try increasing the primary spring's initial tension. That's done by rotating the spring perch on the cam plate.
If you need weights in better condition, ask halifaxhops.