308 GT4 1979 - Aligning distributor Magneti Marelli SM805A with Camshaft

Hello everyone,

I am calling for some help of the community. I am new here as I just bought my Dino 308 GT4 (from Oct 1979) about two weeks ago. Chassis # is 14992.
I had to dismantle the ignition distributor (Magneti Marelli SM805A) because the outer bearing was totally destroyed.


I have the 308 GT4 workshop manual but there is no information related with electronic ignition.
So, I have not been able to identify how to set/align the distributor axis with the camshaft. Also, being French sorry if my english is not perfect.

It is only once I succeeded to open it I discovered that I had the electronic ignition, meaning without contacts.





As I have hard time to find maintenance information about the magnetic pulse electronic ignition with distributor Magneti Marelli SM805A, as tutorials, DIY etc

So I have several questions for you. I hope that someone will be able to answer or at least to point me to the right place to find the information (forum, documentation, etc)
I have found that post ( https://www.ferrarichat.com/forum/threads/rebuilding-the-308-electronic-ignition-sm805a-distributor-marelli-aei200-ignition.435679/ ) but not sure to fully
understand all the discussions.

1/ What is the method to make the correct alignment between the distributor shaft and the camshat ?



When I removed the distributor (single one) from the cylinder head, I realized that it is simply a 22 groove shaft without any location notch.
So the distributor shaft can be introduced in the camshaft in any of the 22 positions. I was hoping that it could be 20 grooves because the 4 tips Distributor Reluctor Ring passing in front the impulse unit would have created a uniform 18degrees increment. But as there are 22 grooves, it makes a unique solution (out of 22, with 16.36° increment).
And as there is no contact, I cannot easily check the opening time with a simple bulb light. How to measure the signal of magnetic pulse (mainly as static) ?

I am making a little tool to correctly apply the 0.3mm distance between the sensors and and the tips of the
Distributor Reluctor Ring

2/ Where are the marks (on flywheel, pulley, etc) to make the alignments with the stroboscopic lamp ?

Thank you in advance for your answers. Emmanuel
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Hello Steve,

Thank you so much for your detailed explanations.
The red little notch in distributor housing that must be aligned with cylinder #1 at PM was the key information that I was looking for.
That's so easy when you have the information.

Regarding the marks on the flywheel, I had found it on my own last night (not that difficult).

PS: your engine is Sooo clean !

Now, I would like to share the technique that I used to make sure that I have exactly (and even for both sides) 0.3mm between the magnets and the tips of the rotor.
I have made a centering tool of 30,6mm diameter that goes into the bearing. The rotor is 30mm so, I just added 2 x 0,3mm to get 33,6mm. I just have to put the magnets in contact of the centering tool then tight the bolts.



Thanks again. I should be able to start the engine tonight without any difficulty !

 

Ooops, I realized that I made a typo:

Now, I would like to share the technique that I used to make sure that I have exactly (and even for both sides) 0.3mm between the magnets and the tips of the rotor.
I have made a centering tool of 33,6mm diameter that goes into the bearing. The rotor is 33mm so, I just added 2 x 0,3mm to get 33,6mm. I just have to put the magnets in contact of the centering tool then tight the bolts.

Here are the dimensions that you would need


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Haha, Thanks. I lived in USA, Michigan for almost 7 years (1995-2001) and I practice my "FrEnglish" every day for my job