Frequently Asked Questions

123 Distributors

123 Distributor and Smiths Tachs

7/6  Q - I understood the issues with wring in the
>> Smiths tachometer and the Crane system in my 67 Volvo but I have no idea what might be
>> required to get it working for the 123 system.  I checked out the123 site
>> and I am guessing that I will need to have my tach modified.

A - No modification to the Smiths tach is required.  The only issue in using the 123 Distributor with the Smiths Tach in a 67 Volvo 1800 is that the wiring instructions that come with the tach, and are on their website, are for cars without tachs. Instead of attaching the black wire from the 123 distributor to the negative terminal on the coil as it shows in the instructions, simply attach it to the white wire that goes from the negative coil terminal, through the tach, to the original distributor. Except for attaching the red wire from the 123 Distributor to the coil positive terminal, the wiring is exactly the same as with the stock distributor.


 123 Distributor Advance Curves

Q -  Trying to pick the right advance curve for the 123 Distributor.
>  I have it set to the B20E position (#9, I think). Initially he timed it
> to 10 BTDC at idle, getting 32 at full advance as advertised. Took it to a dyno place to get the SDS injection sorted out, and
> the guy there advanced it to 15 BTDC basic, which supposedly made better
> power. It then pinged around 3000 RPM.
> Then backed it off to 13 basic, it still pings a little around 3000, and
> it may have lost performance at 4000. Obviously we need a curve
> that advances later and or more. We can tell the more part from the
> instructions, but not the when.

A -

The curves in the 123 distributor are the same as the stock curves for the particular stock engine/distributor selected.  There is a little complication with this as these are the curves for the european models, and they do not always match up with the specs in the English manuals that cover the US spec cars.
Without looking them all up, my recollection is that full mechanical advance is "all in" with most of the stock distributors by 3500 engine rpm, but that the B20 A advance goes well past 4,000 rpm. So you may want to try that, with a lower intial advance setting, to get less at 3000 and more at 4000. 
So try #5 with initial timing set at  6 or 7 degrees.
Have you tried mixing in vacuum advance?
I would go to vacuum advance with the vacuum signal from the manifold in order to get more advance at idle speed. This would allow the mechanical advance at idle to be brought back to less than 10  ( try 6 ) the total mechanical would be less at 3000 and not exceed a total of 32 - 33 deg.  With the vacuum signal for the vacuum advance taken from the intake manifold, opening the throttle reduces the vacuum signal reducing or entirely eliminating the vacuum advance.
So far, with somewhere near 1000 individual dyno runs with B18/B20 engines, we have not found one yet that made better power with an advance of more than 33 degrees.  Most end up being timed with max mechanical advances of between 30 and 32 degrees.