123 Ignition Twin Cam question

[TurboFource]

Since the Twin Cam did not have vacuum advance in the original distributor has anyone programmed it into the 123?

[cazman]

I have not. I don't think it would be beneficial.

[jbcollier]

I did it for my crossflow powered Seven but it has a ported vacuum tap.  You could plumb it to manifold vacuum and set the starting rpm to around 1300.  The advantage of this is that it will allow you to also retard  the ignition when the boost comes on.

[TurboFource]

Thanx for the replies, the Tune+ allows for programming boost retard.

Cazman , would you be willing to share your advance curve that you programmed?

[cazman]

Sure. I have 140 hp, 10.5 compression, sprint cam, stromberg head, idle at 950. I had it on a road dyno and this seems to work well.

You may notice an anomaly at 900 rpm. Sometimes when cold the rmps will drop below my 950 idle, so it advances at 900 to bump it back up. Otherwise, that set point does little.

[TurboFource]

Thanks!! Gives me something to start with!

[TurboFource]

I plotted some Stromberg motor advance curves …. The Fed one looks pretty lazy!

Two are from cars with 123 Ignitions and were on a chassis dyno, one Domestic Stromberg and the last Federal model (based on info from Wilkins book).

[jbcollier]

Mr. T. Force, I highly recommend setting up your particular engine on the dyno.  Your engine is just too much changed from any known configuration to use anything else as a baseline.  You are going to need a VERY experienced dyno operator.  Would hate for it to go bang after all that work.

[TurboFource]

I definitely would hate that!