Guidance Request: S2 Spider Distributor Fiddling - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 3 (permalink) Old 08-28-2014, 01:58 PM Thread Starter
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Guidance Request: S2 Spider Distributor Fiddling

I haven't played with ignition components for decades, the '70s to be precise, and would like a bit more info to avoid heading down a bad path. My goal is to replace what I assume is a traditional ignition points system with an electronic one in my 2L SPICA Spider.

Topic 1: Current distributor identification

From what I've read in various BB threads here it appears that I need to pull the distributor in order to identify it. Is this correct?

Topic 2: Pulling current distributor for identification

Assuming that I do need to pull the distributor, can I just pull it without rotating the crankshaft so that cylinder 1 is TDC? That is, can I just carefully pull it, read its id, and replace it without perturbing ignition timing?

Topic 3: Distributor replacement

Perhaps the most debatable topic in this posting: which electronic system to use?

If money were no object, I would surely go with the 123. However, money matters given the number of pending car projects on my list.

Pertronix is my most likely option, even if I have to drill some holes in the mounting plate. However, how can I determine if my current distributor is a good host? Yes, the car runs now, so the current distributor works. Is there an inspection checklist that I can follow? If necessary, can I overhaul the distributor myself?

Is the Marelli Plex preferable to the Pertronix? And if so, are the Marellis still available?

Are there other electronic ignition options?

Thanks in advance for your advice

1974 Spider
Work gets in the way of my hobbies. Nothing takes just 5 minutes.
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post #2 of 3 (permalink) Old 08-28-2014, 02:11 PM
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Quote:
Originally Posted by BobG View Post
From what I've read in various BB threads here it appears that I need to pull the distributor in order to identify it. Is this correct?
The odds are good you have a Marelli (if the weights are above the points, it's a Marelli - if below, it's a Bosch). But yes, you will have to pull it to read the model number at the base.

Quote:
Assuming that I do need to pull the distributor, can I just pull it without rotating the crankshaft so that cylinder 1 is TDC? That is, can I just carefully pull it, read its id, and replace it without perturbing ignition timing?
Yes, you need to remove the distributor to install the electronic thingy. Yes, you can pull the distributor without rotating the crankshaft. But no, you can't replace it without checking the timing. Substituting the electronic trigger for the points is going to change your timing somewhat. And even if it didn't, you can't re-install your distributor exactly the way it came out. Plus, you will want to add a little more advance when going with electronic ignition.

Quote:
Pertronix is my most likely option, even if I have to drill some holes in the mounting plate. However, how can I determine if my current distributor is a good host?
I believe a Pertronix is available to fit your Marelli distributor without drilling any holes. Several BB threads have discussed this, like the one at: http://www.alfabb.com/bb/forums/gt-1...de-73-gtv.html. Or check out p. 6, which is the 8th page of the pdf file at: http://www.pertronix.com/catalogs/pd...tronix2012.pdf

Quote:
Is the Marelli Plex preferable to the Pertronix? And if so, are the Marellis still available?
I don't feel that the Marelli Plex preferable to the Pertronix. Just finding one will be tough; they haven't made those things for 25 years or so. If you do find one, it's going to be used, so it may have broken wires, etc. Don't get me wrong - back in its day, the 'Plex was state-of-the-art - but now, it's a "period accessory".

Quote:
Are there other electronic ignition options?
Sure, lots. But if you are on a budget, it's hard to beat the Pertronix.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 08-28-2014 at 03:49 PM.
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post #3 of 3 (permalink) Old 08-29-2014, 07:56 PM
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Jay has listed the pro's of switching to Pertronix. The con is that you may have mechanical wear in that old Marelli so while eliminating the points you still have a docile advance curve that may have a lot of variability.

The advantage of Marelliplex is that it is simple, robust and has a high energy coil that will produce hot sparks. A friend uses one on his 220 HP Spider race car. The downside is that they are old and may have as much wear as your current marelli and the unmodified ones had poor advance curves.

The advantage of the 123 is that the advance curves are digital and are accurate and have almost no variability. The downsides are cost and they will not directly fire a high energy coil. A 123 with a Bosch red coil is a pretty good combination for a road car.

Ed Prytherch
79 Spider
76 Suzuki GT500
2011 Jaguar XKR

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