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Discussion Starter #1
Hi. Let me start by identifying my current set up. 81 US model Spider with Marelli Plex ignition, converted to webers, Euro cams, Euro intake and IAP header by po. 5 years ago when I bought the car I replaced the ignition module with a Delphi and the coil with a Pertronox Flame Thrower. Car runs really good and starts easily. I'm just considering playing around with the ignition to see if I can tweak a little more performance out of her but not spend a lot or replace the entire dist.
Wondering if anyone has experience with any of the "performance" ign. modules from accel or msd or pertronox etc. with the Plex system. Also would like to hear of any experience or advice on replacing the weights or springs in the mechanical advance within the dist such as the Moroso 72300 kit
Thanks for any help
Steve
 

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@Steve88D, Years ago Alfa Ricambi in CA sold modified MarelliPlex distributors with more aggressive advance curves. I'm not sure if they changed the springs or the weights, or both. Somewhere you might be able to find the specifications. Try to find a shop that still has an ignition distributor testing machine like a Sun 504. Of course you will also need an assortment of springs and weights. Good luck! Distributor Testing Service
 

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The stock GM HEI modules were good but I imagine most replacements come from China so who knows about the quality. A stock module will limit coil current to 5 amps which is sufficient to make good sparks in a 4 cylinder engine beyond the rpm at which you are making power. I have read posts that suggest Accel modules are "better" but I have never seen any independent data to support those claims. I have tested aftermarket HEI modules, no name brand, bought on ebay and they performed to specification. The variable dwell angle and current limiting were both correct. It is important to use good heat transfer grease when you install a module as overheating will definitely shorten the life.
For comparison, A Bosch ignition module as fitted to GTV6 and Milano's limits current to 6 amps, as does 123ignition distributors so they can give you about 20% more spark energy.

Fitting weaker springs will allow the distributor to advance more quickly which should give better throttle response and fuel consumption but you have to deal with unstable idle and/or detonation at mid rpm if you advance too quickly.
 

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Discussion Starter #4
Thanks andylarry for your suggestions and alfaparticle for your technical details. I used Arctic silver when I installed the Delphi module as I knew heat transfer was critical. I certainly noticed quicker starts and better midrange power delivery after installing the new module and coil and all that I have read on the Marelli Plex system tells me it's pretty good. Was just trying to decide if a little tweaking and a few dollars upgrading this system would actually get any performance results. Any experience out there with the Moroso 72300 kit I mentioned ? It includes new weights and 3 pairs of springs allowing you to adjust how quickly maximum advance it achieved
 

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To get the best out of a plex the coil should be 0.5 to 0.7 ohms primary.
 

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Discussion Starter #6
Yeah, when I bought the coil I got the lower 1.5 ohm they had. I have seen a thread on here where a member used an MSD CD coil in a Plex system with good results
 
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