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Folks,

Happy Sunday! I apologize for what I’m sure will be a simple question, but I just wanted to double check my connections for this new (to me) 123 distributor.

Alfas are still new to me and I haven’t worked on anything before with a coil quite like this Magneti Marelli. For anyone who knows, do I simply land the 123 black and red on the coil - and +, respectively, as the 123 instructions call for? The extra wiring on this coil just has me second guessing and leery of setting those wild electrons free in the wrong way.

Any confirmation would be appreciated before I put power to this. Thanks, all!
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The red box is a ballast resistor I believe. If the instructions say to connect to the + and - I would use the terminals on the top of the coil.

Sent from my GM1917 using Tapatalk
 

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The red box is a ballast resistor I believe. If the instructions say to connect to the + and - I would use the terminals on the top of the coil.
Yes, the red "box" is the ballast resistor. I'm no expert on 123's, but I don't think they are intended to work with ballast resistors. So as archeologist advises, you should probably just disconnect the resistor by hooking the green/black wire to the coil "+" and not using the wire from the starter (looks to be solid green).

A bigger question is whether the Marelli coil has the right resistance to work with the 123. The documentation that comes with it should specify what ohm coil to use. I've heard of pairing Bosch red coils with 123's; dunno about Marellis.
 

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Yes, the red "box" is the ballast resistor. I'm no expert on 123's, but I don't think they are intended to work with ballast resistors. So as archeologist advises, you should probably just disconnect the resistor by hooking the green/black wire to the coil "+" and not using the wire from the starter (looks to be solid green).

A bigger question is whether the Marelli coil has the right resistance to work with the 123. The documentation that comes with it should specify what ohm coil to use. I've heard of pairing Bosch red coils with 123's; dunno about Marellis.
The 123 is quite a system I paired it with a low resistance 1.5 ohm flame thrower coil,
 

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The 123 ignition requires a total impedance of at least 1 ohm. A quick search of the BB says those old Marelli coils have a primary resistance of about 1.5 ohms. I would measure it to confirm. If that is the case, you don't need the ballast resister. Disconnect the green wire from the coil (+) and connect the green and black wire in its place.

BTW, the 123 ignition works fine with ballast resistors. The key is the total impedance. I followed alfaparticle's (Ed Prytherch) lead and use a low impedance MSD Blaster 2 coil and a 0.8 ohm ballast resister with the 123 in my '78 Spider for a total primary resistance of about 1.5 ohms.
 

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Rich is correct
 

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Mark,

I'm not that well versed on Coils and Distributors, but I learned one thing. Getting a new cap and rotor for these things isn't easy. Try going to the local Autozone and ask for a Beru VK105 cap and rotor, and you will get a "What year and model is your car" .

If you go to the local Porsche Boutique (Can't call them dealerships anymore) and ask for a cap and rotor for a 356 one of the oem uses, and they have to order it from Deutschland. I was off the road for 3 weeks trying to track it down.

I found mine from FCPEuro online. Cap and rotor for less than $15. I should get a spare set to keep in the trunk with my spare Spica belt and other things you wont find at Autozone.
 

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You save about $30 every 20K miles and risk getting something that is not OEM. You should be shopping at Vick Auto.
 

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These are OEM. 123 uses BERU parts.I just got them from elsewhere.

I have ordered from Vick, good prices (especially on the fuel tank), but prefer Centerline for the telephone service.
 

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Here is the circuit for obtaining the maximum spark energy from a 123 distributor. The coil is an MSD Blaster 2 with a resistance of about 0.7 ohms and the resistor is an MSD ballast resistor of about 0.6 ohms. This is better than a 1.3 ohm coil in two ways:
1 - Blaster 2 coil has a lower inductance which improves spark energy above about 3000 rpm
2 - the relay ensures that the coil and resistor get full battery voltage.
 

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Here is the circuit for obtaining the maximum spark energy from a 123 distributor. The coil is an MSD Blaster 2 with a resistance of about 0.7 ohms and the resistor is an MSD ballast resistor of about 0.6 ohms.
So you don't bypass the resistor when the starter is engaged, as is typical with resistor & coil setups. Which makes sense, as you don't want the inductive "kick" from the starter solenoid damaging the electronics in the 123.

Is the relay really necessary? I understand that it eliminates the voltage drop resulting from routing the coil current through the ignition switch contacts and all that wire & connectors. But couldn't you achieve the same voltage at the coil by using a .5Ω resistor (say) without the relay instead of the .6Ω with? I dislike adding components such as relays to critical circuits such as the ignition - just one more thing to fail.
 

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The 123 ignition requires a total impedance of at least 1 ohm. A quick search of the BB says those old Marelli coils have a primary resistance of about 1.5 ohms. I would measure it to confirm. If that is the case, you don't need the ballast resister. Disconnect the green wire from the coil (+) and connect the green and black wire in its place.

BTW, the 123 ignition works fine with ballast resistors. The key is the total impedance. I followed alfaparticle's (Ed Prytherch) lead and use a low impedance MSD Blaster 2 coil and a 0.8 ohm ballast resister with the 123 in my '78 Spider for a total primary resistance of about 1.5 ohms.
 

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The relay is not necessary but it increases coil current by eliminating voltage drops and hence spark energy. I would be reluctant to bypass the resistor on starting because of the risk of damaging the 123 distributor.
I posted some graphs a couple of years ago showing coil current for various coil and distributor combinations and they show the advantage of the MSD coil/ballast resistor combo.
 
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