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Is there an advantage to a different plug gap to use with these?
 

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Yes, My Ti Super Rep has a 123 distributor coupled with a Lucas DLB105 sports coil. and I've experimented with various plug gaps. I use the NGK Iridium plugs equivalent to the standard NGK B7ES, and the "standard" 0.030" is too narrow a gap. I tried 0.040", and it was much better. (with a fancy coil you can use a bigger gap than this). However, I found the best gap for my set-up was 0.035".. I get zero plug fouling, very clean pick-up, and instant starting in Winter after 4 pumps on the accelerator. In summer I only use 2 pumps to start. The 2 litre engine was completely rebuilt about 6000 miles ago and is like a sewing machine.
The 123 electronic, plus a decent coil means that the spark generated can jump a bigger gap, and mine runs smoother, and the plugs are a much better colour, combined with no fouling.
All engines are different, so best to experiment with gaps to find out what's the best for your motor.
 

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Let's get things in the proper order: it's the coil that provides the energy to jump the plug gap, and how strong a coil you can use is dictated by what your ignition system is able to switch without suffering. 123 ignition recommends to stay with a coil that has a primary internal resistance of 3 ohms at least. The Bosch blue coil, the Lucas sports coil both are rated at 3 ohms. The Marelli coil originally supplied on 2000 Alfas with point ignition has a lower resistance but is paired with a ballast, which achieves the same thing.

Electronic ignition mostly provides a more accurate and stable timing control than points. As a bonus, they allow a little bit more dwell time than points, with allows the coil to recharge closer to capacity. For ultimate spark power, a different system than 123 ignition is required. But who needs that for the street?
 

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123 ignition recommends to stay with a coil that has a primary internal resistance of 3 ohms at least.
Where did you read that? My literature says 1 ohm. I have been using a 123 distributor with a 0.7 ohm coil + a 0.7 ohm ballast resistor for many years. A few years ago I posted graphs of coil current versus rpm for a number of coil + distributor combinations and this combination is impressive. Remember also that the 123 modulates dwell angle from about 10 degrees at low rpm to 70 degrees at high rpm to get the best out of the coil without overheating it.
I am currently using .050" plug gaps with the same type plugs as GTA R. I started with .040" and there was a definite improvement in driveability with the larger gap. It has nothing to do with being a street or race motor rather the ability to reliably ignite lean mixtures. My Wbers are set up about as good as they can be but it is possible to find a lean spot which can result in a hesitation. The larger plug gaps have helped eliminate that.
Most modern cars run with gaps of about .040" so that they will reliably ignite the lean mixtures that are used to achieve good fuel consumption and low emissions.
 

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Discussion Starter #5
Thank you guys!
Ed, I went with your recommended coil setup. I will start with .040 and see how it goes.
As an aside, the 123 is so much more responsive I have an occasional problem, in a good way, with tire spin on marginal surfaces.
 

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Where did you read that? My literature says 1 ohm.
Ooops. Quoting from memory. Either 123 changed its spec over the years or whatever. If they say 1 ohm, then that's the way to go.

EDIT: I've checked 123's website, that's the source of the confusion. They do say 1 ohm is OK, but follow to recommend a Bosch blue coil which is 3 ohm.
 

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The potential downside of having a large plug gap is that there will be insufficient energy to fire it at high rpm. My motor makes buckets of power all the way to 7000 rpm. It is not limited by spark energy or plug gap.
here is a post comparing spark energy between a Bosch blue coil and a Blaster coil + ballast resistor:
1628608
 

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Interesting...
I’ve recently installed a Flamethrower 3ohm coil into my 1600, with original style points in 041 dizzy.
I’d been getting plug fouling for a while. I’ve read warnings about bigger plug gaps putting excess load on points, cap contacts etc, but that pushing the gap out by .003 is safe.
Standard gap is .020. I’ve gone to .023. How far (Wide) can I safely experiment?
(Changed to B6ES, float heights good and I have carb kits coming next week in case I’m chasing the wrong fix.)
TIA.
 

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You can open the gap until you get misfiring at high rpm provided that your cap, rotor and HT wires are in good condition. I doubt that it will have any effect on the points.
You can see from the blue curve above that available spark energy falls with rpm.
 
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