Ok, if I'm running a 123 dizzy do I set the gap wider like I would for electronic ignition or do I set it at the standard 25 thou. It's a mild mk 1 cooper motor with twin 1 1/2 " SU's and LCB exhaust and bp5es NGK plugs if that makes any difference.

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if it starts that is good enogh for me , if your worried about power get it dynod

If you're coil isn't up to a larger gap, then no. If it's running a standard coil then it probably won't like the extra work you put onto it. But more importantly, check with the maker as to the type of coil it is rated to operate with, the primary current from the battery may be too much for the electronics if you don't check first.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

It's running a GT40 coil, I've run it with a big gap 34thou and a standard gap 25thou, I can't really tell any difference in running condition or performance but I was just wondering what it should be.

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As you open the gap up, it will take a little longer for the coil output to rise to the higher voltage needed to make the jump at the plug. So check your timing as a matter of course.

If you open the gap up too much, it will either not fire at all, or find another path down to ground (dirty dizzy cap, old leads, rotor button etc) because the of the higher voltage generated. If it works and doesn't break down under load, then it's all smiles.

The benefits are a longer bigger spark which apparently gives you a better burn, emissions and hence economy. But it's not HP producer on it's own.
However, it might make it harder to start on a cold morning (if it can't spark for a normal gap, why would it spark for a larger one?) because the increased starter motor load reduces the output voltage by a large margin, maybe thousands of volts depending on how cold the weather is and the condition of your battery..

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks Mick. BTW I really like your car.

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Yours is nice, it's like Simon's but is shiny.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

I run a GT40-R coil with a Nissan Pulsar electronic dizzy, it will fire them OK up to .040" gap. I set them to .034".

Keep opening them up, eventually it will misfire during acceleration. Then reset them to .006" or so less.

Bigger gaps give a fatter spark (if the ignition system can handle it) and potentially better economy... one reason most modern cars use a 0.040" gap.

<edit> typo

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I have mine set to .028" with a 123 dizzy and Bosch GT40 coil, and it starts well, runs well and gets good economy.

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Simon

The adventures of an owner builder in the Tallarook Ranges