123 Distributor / Setting timing Options

[rjames]

For those that have a 123 Distributor, I need some help setting my timing. I'm probably over thinking all of this but I've read several different threads on setting the timing with this distributor and I have interpreted them all differently.

I'm running a stock 2.0 w/ DJet.
The 123 distributor setting I'm using is 'B' (negative advance), and has a max advance of 22 @ 2700 RPM.

With my new-school timing light that allows me to set the advance, (with vacuum line from the tb plugged) do I:

- Set timing light to 27 advance and rev to 3500 RPM and time to the TDC mark?
- Set timing light to 0 advance and rev to 3500 RPM and time to 27 degree mark (same as above, right?)
- Set timing light to 22 advance and rev to 2700 RPM and time to TDC mark?
- Something else? (IMG:style_emoticons/default/rolleyes.gif)

I feel like an idiot asking this question. Timing is such a basic thing and I had no problem with the stock distributor and an old school timing light, but I've read more than one thread on how to time with the 123 distributor, plus I've also read that there's 10 degrees advance added at static on these distributors.
Help!

[rjames]

I have the vacuum port on the dizzy connected to the manifold vacuum port on the TB which is used to retard timing at idle. Using setting ‘b’ which is the correct setting for the stock dizzy the 123 dizzy replaced. Setting ‘b’ does not use vacuum advance.
Stock djet with correct parts. Smog stuff has been removed. Idle was 900 with the stock distributor.

I am hoping that someone can explain why when the max advance on the 123 dist is 22 degrees I still time to the 27 mark.

[914_teener]

I have the vacuum port on the dizzy connected to the manifold vacuum port on the TB which is used to retard timing at idle. Using setting ‘b’ which is the correct setting for the stock dizzy the 123 dizzy replaced. Setting ‘b’ does not use vacuum advance.
Stock djet with correct parts. Smog stuff has been removed. Idle was 900 with the stock distributor.

I am hoping that someone can explain why when the max advance on the 123 dist is 22 degrees I still time to the 27 mark.

Understand your TB has a manfiold vacuum port.

The 123 curves are supposed to mimic the stock distributor curves and if it is maxed out for curve B at 22 degrees why are you using curve B and why are you timing to 27 degrees? Do you want it to behave like a stock distributor to limit idle emissions? What "smog stuff" did you remove? Sounds like your car is post 74.

Before I installed my 123 I found Brad Anders bit on stock dizzies extremely helpful:

https://members.rennlist.com/pbanders/distributor.htm

[rjames]

I have the vacuum port on the dizzy connected to the manifold vacuum port on the TB which is used to retard timing at idle. Using setting ‘b’ which is the correct setting for the stock dizzy the 123 dizzy replaced. Setting ‘b’ does not use vacuum advance.
Stock djet with correct parts. Smog stuff has been removed. Idle was 900 with the stock distributor.

I am hoping that someone can explain why when the max advance on the 123 dist is 22 degrees I still time to the 27 mark.

Understand your TB has a manfiold vacuum port.

The 123 curves are supposed to mimic the stock distributor curves and if it is maxed out for curve B at 22 degrees why are you using curve B and why are you timing to 27 degrees? Do you want it to behave like a stock distributor to limit idle emissions? What "smog stuff" did you remove? Sounds like your car is post 74.

Before I installed my 123 I found Brad Anders bit on stock dizzies extremely helpful:

https://members.rennlist.com/pbanders/distributor.htm

I appreciate all of the responses.
Yes, my car is a '75 and only has the manifold vacuum port which was used for retarding the timing for emissions as I understand it.

Why am I timing to 27 degrees? Because most every thread I've read on timing a stock Djet with the 123 dizzy says to time it to 27 degrees. But that's really the basis of my question- why 27 if the max advance on the 123 dizzy is 22? I also just learned that max advance on my stock distributor is also 22. (039 905 205 A in the chart below) So I guess now it's a general question of why do we time our engines to 27 if max advance is 22?


And I'm using setting 'B' in hopes of getting the idle down to 900-1000 RPMs instead of the 11-1200 it sits at now. That said, using setting 2 on the dizzy and not using vacuum off of the TB (and plugging the TB vacuum port) yields the same result. Both 'B' and '2' settings match the stock dist that the 123 replaces.

Car runs great otherwise, but the high idle sucks. The only way I've been able to bring the idle down is to over richen the air/fuel mixture, which I don't want to do.