Quote:
Originally Posted by PNW Targa
I'm working my way through the plugs, points, timing and dwell. Plugs have a lot of carbon fouling. Not sure how much is due to modern fuel (though I have access to ethanol-free premium) or a too-rich mixture. Will replace and monitor. Next up is to check the timing and dwell. Working on finding a 13mm wrench for the distributor that's functional, given the limited clearance.
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First and foremost from my point of view - the mixture is the main reason for carbons at the spark plugs after the wrong heat range of the plugs. So make sure that you're using the specified spark plugs for the engine. But also how you're driving the car. Cruising for ages at low speeds and rpms causes that plugs won't reach their self cleaning temperatures.
https://www.championautoparts.com/Parts-Matter/automotive-repair-and-maintenance/how-to-read-spark-plugs.html
https://ngksparkplugs.com/en/resources/read-spark-plug
https://am.denso.com/plug-global/basic/select/
https://www.denso.com/global/en/products-and-services/automotive-service-parts-and-accessories/plug/basic/heatrange/
Sooted plugs were one of the reasons why Porsche introduced the CDI ignition system because it generates way more ignition power to break soot to ensure a proper combustion under any conditions. Carreras with a much more precise mixture control run leaner than CIS and carbureted cars. So they run fine with transistorized igntion systems.
Todays 123igniton can create almost the same ignition power as the CDI, especially with a igniton booster like the
"BigFatSpark" module which is basically nothing else as a common ignition amplifier module from the 90ies. 123ignition also provides high power ignition coils, so they can waive a amplifier module.
Concerning your interest in upgrading your ignition to a 123ignition I suppose to think about this variant:
Afaik the CDI on the early 911 - as yours too - the CDI is triggered with breaker points. 123 dizzys are basically nothing else as a transistorized ignition mimicking breaker points. (Only SCs used magnetic pickups in their dizzys whose also required other CDI boxes to manage that signal.)
So you can still use the CDI box from your car, but replacing the dizzy with the 123. Instead of connecting the coil direct to the trigger output of the 123, you can use the signal to manage the CDI box, so that the coil is connected to the CDI box again as the original setup...with this approach you have the best of both worlds: Still CDI, but a modern microprocessor controlled and programmable ignition timing with a new dizzy...
I successfully tested this variant lastly on the workbench with a Permatune CDI GS (general service) box which was intended to be used on cars other than 911. But still 911 box should the job as well if it can use breaker signals...
Keep in mind - this approach won't work with SC dizzys!
Thomas