Reply to "Delay Mechanical Ignition advance"

Something you could try is using manifold vacuum rather than venturi vacuum to operate the vacuum advance.

This is a little outside normal practice and requires a rethink of how your advance works but can sometimes be the way to go.

What it would do is: reduce ignition advance by the vacuum advance amount (say 16 degrees) while cranking, so making starting easier.

Once it fires up it will immediately advance 16 degrees, so you will have initial advance (say 2 degrees) plus 16 = 18 degrees.

When the engine speeds up to what ever your centrifugal settings are the centrifugal advance (say 20 degrees) will be added to the 18 to give 38 degrees total.

Now if you floor the gas pedal regardless of the engine speed and the manifold vacuum drops to 0, as it would under high load, the 16 degrees of vacuum advance instantly gets removed from the total advance, regardless of the initial advance and centrifugal advance settings.

As manifold vacuum increases as the engine overcomes the load the advance increases.

This reduces advance just when the engine is prone to detonating and advances it to the maximum when conditions allow a maximum amount of advance.

All the parameters of advance can be under your control.

You can adjust initial advance by rotating the distributor (remember to add what the vacuum will add when the engine starts).

You can adjust degrees of vacuum advance by modifying the vacuum advance mechanism inside the distributor and you can modify the centrifugal with the springs and weights as you suggested.