Base timing. Really ?
I'm going to guess 16 to 18* Distributor starting point for a curve
If the combustion chamber conditions at idle have little heat, it will need more and vica versa.
Get it warmed up and see if you can get it to idle with good stability at 18*. Then see if it will run just as well with 17 or 16, or maybe it needs 19*. Whatever timing it needs to run decently without too much throttle opening. Too much throttle opening is idling with the primary throttle plates revealing more than .035 or .040" of transfer slot to the intake manifold.
For high rpm use and most electronic ignitions, allowing for an additional 2 to 4 degrees in the advance will help in the upper rpms.
In this way we use the mechanical advance to offset the time lost in the electronic switching. (If not racing then not so important.)
For example lets say the distributor in hand mapped out to have a timing like this
Its a handy one for the example because the factory initial was TDC.
We see by the timing light it has 32* advance. Lets pretend this was a electronic distributor. In which case the advance plate would have something more than 16* in the slots.
Lets say we weld up the inside of the slots enough to get 18 degrees of advance.
If the engine still can idle at 700 rpm, then yes the advance will be delayed.
If you can get your engine to idle that low, great!
If you can get it to idle at 750 or 800, that will be good too.
If its a little higher, don't sweat it.
Regardless, if the advance isn't starting until several hundred rpms above idle, the spring to adjust is the light spring.
(I call it the primary spring because it controls the initial portion of the advance.)
Before going through the trouble of finding a different spring, experiment with reducing the initial tension as shown in this post
That will bring the advance in sooner.
Advancing the initial to 17* at 800 rpm, the curve shifts up.
That seems reasonable for slightly warmed 440, for your engine I'd would start higher.
I'm going to guess 16 to 18* Distributor starting point for a curve
If the combustion chamber conditions at idle have little heat, it will need more and vica versa.
Get it warmed up and see if you can get it to idle with good stability at 18*. Then see if it will run just as well with 17 or 16, or maybe it needs 19*. Whatever timing it needs to run decently without too much throttle opening. Too much throttle opening is idling with the primary throttle plates revealing more than .035 or .040" of transfer slot to the intake manifold.
Yes if you know for sure 35* is the maximum advance the engine will want.
For high rpm use and most electronic ignitions, allowing for an additional 2 to 4 degrees in the advance will help in the upper rpms.
In this way we use the mechanical advance to offset the time lost in the electronic switching. (If not racing then not so important.)
Welding up the inside of the advance would make the advance start a little later if everying was stock.
For example lets say the distributor in hand mapped out to have a timing like this
Its a handy one for the example because the factory initial was TDC.
We see by the timing light it has 32* advance. Lets pretend this was a electronic distributor. In which case the advance plate would have something more than 16* in the slots.
Lets say we weld up the inside of the slots enough to get 18 degrees of advance.
If the engine still can idle at 700 rpm, then yes the advance will be delayed.
If you can get your engine to idle that low, great!
If you can get it to idle at 750 or 800, that will be good too.
If its a little higher, don't sweat it.
Regardless, if the advance isn't starting until several hundred rpms above idle, the spring to adjust is the light spring.
(I call it the primary spring because it controls the initial portion of the advance.)
Before going through the trouble of finding a different spring, experiment with reducing the initial tension as shown in this post
That will bring the advance in sooner.
Advancing the initial to 17* at 800 rpm, the curve shifts up.
No. The heavy spring has a long loop in it. This spring has no effect on the first part of the advance. Its the secret sauce of the two stage advance. ;)
