Advance spring
Concept:
Its best to let the mechanical advance compensate for changes in combustion that change with rpm.
Then use vacuum advance for changes in fuel density.
The reason for vacuum advance is to compensate for slower burning conditions. In particular leaner, less dense mixtures above idle rpm. Lean conditions are prefered for maximum efficiency and power during light and mid-throttle. Chrysler illustrated that - see this
In practice:
An LA with 4 bbl will work well with mechanical timing that looks similar to this
A 360-2bbl timing probably looks roughly like this. Without knowing the distributor number and having the shop manual, really don't know what the distributor has in it.
Alot of unknowns with the new distributor and two light springs, but even a very fast advance can be OK at WOT. Especially on a cold engine.
In fact for drag racing it is often preferable.
But it will ping at part throttle when used with vacuum advance.
it will also ping at very light throttle when the engine is fully warmed up.
Using a heavy spring with long loops is the secret to shaping the curve to avoild part throttle ping.
It also helps power at very high rpms but thats another story.
A timing curve shaped as shown in violet illustrates the effect of one light spring and one long looped spring.
.
Concept:
Its best to let the mechanical advance compensate for changes in combustion that change with rpm.
Then use vacuum advance for changes in fuel density.
The reason for vacuum advance is to compensate for slower burning conditions. In particular leaner, less dense mixtures above idle rpm. Lean conditions are prefered for maximum efficiency and power during light and mid-throttle. Chrysler illustrated that - see this
In practice:
An LA with 4 bbl will work well with mechanical timing that looks similar to this
A 360-2bbl timing probably looks roughly like this. Without knowing the distributor number and having the shop manual, really don't know what the distributor has in it.
Alot of unknowns with the new distributor and two light springs, but even a very fast advance can be OK at WOT. Especially on a cold engine.
In fact for drag racing it is often preferable.
But it will ping at part throttle when used with vacuum advance.
it will also ping at very light throttle when the engine is fully warmed up.
Using a heavy spring with long loops is the secret to shaping the curve to avoild part throttle ping.
It also helps power at very high rpms but thats another story.
A timing curve shaped as shown in violet illustrates the effect of one light spring and one long looped spring.
.