I had the 1-2-3 installed last week and the performance is noticeable improved; based on the chart below, what would be the difference between Curve 2 and Curve 3 ?

My '75 L-Jet has the 2L crank, 96mm Pistons, and a larger Vanagon TB

So, it feels good on curve 2, what might happen going to curve 3 ?

Okay. I am not an ignition expert, but the max advance/RPM figures are interesting. On my 76 2.0L I always set the timing at 27 degrees at 3500 RPM (per the Haynes manual). The above chart indicates max advance figures of 22 or 23 for the various 914 options. With the 1-2-3 distributor, can the max advance be adjusted upward? How about the shape of the advance curve?

IIRC, Ed at 1-2-3 said one has to add 10 to those max advance figures. Not sure of the reasoning, but that was communicated to me.
I had my local Indy do the conversion, so i’m Not up on any of the details.
The car runs smoother, nice mid-range RPM performance, no pinging so far, and temps are satisfactory.

You add 10 because that's the static timing set for the engine. In other words the distributor is set at 10 degrees without any advance being added to the timing at idle. As rpm starts going up the distributor starts adding in advance.

Thanks for the clarification - learned something today

I’m not an expert and am trying to understand before installing my 1-2-3. But if you’re set to curve 2 which has a max advance of 22 degrees and your static timed at 10 degrees that gives you a total advance of 32 degrees which from what I’ve read is too much. I’ve read to keep total advance in the 28-30 range.

Timing advance is stated in relationship to engine revolutions or rpm.s which is timing.

From the 123 chart and to Jim,s question, curve 3 will add 1 more degree of advance up to 3400 rpms instead of 2700 rpm.

So a slighty different curve.

Would curve 3 be more appropriate ?; and, can the curve selector be accessed while the distributer is mounted ?

is the vac connected or are you running with out, i cant remember what you are doing,
i am running #3, with vac.,

Depends Jim.

Stock cam?

I think you may be able to access the dip switch in the car with a mirror and screwdriver...other wise you'll have to stand on your head to see it. The writing is pretty small.

I would try it, but hook up a timing light to confirm along WITH a wide band to make sure you are not running lean to make sure temps are under control.

You might net some top end power if the mixture is right. Only way to know is on a dyno and with a wide band.

I noticed a tremendous difference in mid range and part load with the vac hooked up. Meaning differences of throttle responsiveness (seat of the pants). This is with the stock cam.

If you use the vaccum advance make sure it ported vaccum and not manifold vaccum. The two sources are not the same.

Non-Vac distributer and no port on the rebuilt Vanagon Throttle body
I am hesitant to make any changes; I inquired mainly to learn a little more, and thanks for all the responses.