Duraspark dizzy performance recurve.

[waypastcrazy]

This recurve is to show how to do it not as a fit all application deal.Because each application has its on base timing requirements and full advance timing requirements.Different head chamber designs,compression ratios,bore sizes,head material,cubic inches,nitrous etc etc have different timing requirements.
First i would like to say the vaccum advance is not the full advance mechanism.The mechanical advance inside the dizzy is.The vac advance is for low rpm loads and part throttle loads such as pulling an incline at low rpm in high gear etc.(fuel economy).Where the rpms are not high enough to activate the centrifugal (mechanical advance) completely.The vac is to low or none existent when the throttle is wide open for it to work.That is where the centrifugal (mechanical) is working compltely.I do not use it in performance applications.It is a pita to get it set correctly.Most have an adjusting screw inside vac hose connector if you want to use it.Just run it up till your engine pulls strong under a load at lower rpms than the centrifugal advance activates fully.BE prepared to chase your tail trying to get it and the mechanical to work together.lol
What I have found to work great in daily driver/hotrod is disconnect vac advance completely.Play with different spring tension on the centrifugal advance so that it gives the correct timing needed under different driving conditions.



I am not going to show every little screw.If you have mechanical abilities you can figure out how to remove a few little screws.lol

The key is to figure out where you want your base timing (static) at idle and full advance timing then do the recurve accordingly to acheive this.

FULL ADVANCE
The general rule of thumb is naturally aspirated 9.0 to 9.5 Static compression ratio engines need around 38 to 40 full timing 9.5 to 10.5 35 to 38 and 11.1 plus no higher than 35 degrees.

BASE TIMING
Static timing or what we refer to as base timing at idle with vac advance unhooked.depends on engine build.But the camshaft in general dictates the rpm and base timing.
Genaral rule is
270 dur 600 to 800 rpm @ 10 to 12 degrees timing
280 dur 900 to 1000 rpm @ 12 to 14
290 dur 1000 to 100 rpm @ 14 to 16
300 dur 1100 to 1200 rpm @ 16 to 18
310 dur 1100 to1400 rpm @ 18 to 20


EXAMPLE
I want 12 degrees base timing and 38 total.
38-12=26 then I would need my centrifugal to advance 26 degrees total.
This engine I am working on is 9.8 static compression and a 270 dur cam with factory iron heads.My experience tells me i will be close with this timing.But you will have to figure out what your engine likes then recurve to make it work.

Ok now down to business.
1.Once you have the cap and rotor button removed.Remove the vac advance arm and the 2 screws that hold the vac canister to dizzy housing.

2.Remove the 2 screws holding the gromet the electrical wires pass through.

3.Remove the dowel pin that holds the reluctor on the dizzy shaft.Just use a punch to tap it down underneath the reluctor.Then remove the c type clip from inside the center of the shaft.


4.Pry the reluctor off shaft.Be careful not to pry on the teeth put screw driver or pry bar under the main body of it.mark this because it does go on 2 different positions and if installed wrong your dizzy could be out of phase.