Unhappy 360 (At idle)
The comment about softer distributor springs puts us on alert that the timing at idle might be extra sensitive.
For example, lets say the factory timing looked like this when set at 750 rpm to 12*BTDC.
With the mechanical advance as shown above, the spring force is high enough that advance only just begins around 700 to 750 rpm. Its not going to make much diffence whether the initial timing was set at 600 or 750 rpm.
But lets say the light spring was replaced with one that is 'softer.' If the initial tension was not increased, the weights will now have less restraint and start moving out at lower rpm. Timing at 650 rpm would be different than timing at 750 rpm.
If you have the shop manual, look up the advance specifications in the back of the ignition chapter. Otherwise will need to find someone with a specification card. Maybe @halifaxhops was one for a 79 360 in light truck.
The comment about softer distributor springs puts us on alert that the timing at idle might be extra sensitive.
For example, lets say the factory timing looked like this when set at 750 rpm to 12*BTDC.
With the mechanical advance as shown above, the spring force is high enough that advance only just begins around 700 to 750 rpm. Its not going to make much diffence whether the initial timing was set at 600 or 750 rpm.
But lets say the light spring was replaced with one that is 'softer.' If the initial tension was not increased, the weights will now have less restraint and start moving out at lower rpm. Timing at 650 rpm would be different than timing at 750 rpm.