There was some discussion recently about distributors in my ultrasonic cleaner post and in particular about the springs on the bob weights as on the original 500 distributors the two springs had different ratings to give the right centrifugal advance characteristics. There is only one type of spring available now. I have 5 126 distributors totally stripped down at the moment, Zelmot and another maker, all made under licence fro Magneti Marelli. I got my micrometer on the springs and the wire gauge was the same on each pair.
Also I know from other distributors that the amount of mechanical advance is normally stamped onto the bob weight base plate. Most have 9 degrees but one Zelmot has 10 degrees 30 seconds On it. May be a coincidence but the spring wire was also 2-3 thou thicker. This amount of advance obviously pushed the design to the limit as the outer edge of the bob weights had rubbed very slightly on the inside of the distributor body.

^^ Very interesting.

I've encountered 3 different ways of achieving different springs in distributor advance mechanisms - 1) springs with different wire thicknesses, 2) springs with different number of coils (have you counted the no. of complete turns?),
3) springs with different lengths, one spring has normal round end loops, the other longer spring had one round and one 'U' shaped end loop, this 'U' loop means that the advance weight can move outwards a certain amount before this spring starts to stretch. (important not to try to eradicate this designed-in slackness by e.g. squeezing with a pair or pliers).

Another thought on possibly obtaining more info on distributor springs:-

You might try contacting www.distributordoctor.com to see if they can help with info re. measuring/determining strength of these springs and the various factors involved in their correct selection. Although this company specialises in rebuilding/properly testing Lucas distributors and have vast stocks of Lucas dist. springs, they might possibly? be able to help with Fiat 500 dist. springs or advise on same. (iirc the boss is ex-Crypton U.K. Diagnostic Equipment and is likely very familiar with other makes). This website is worth a read particularly what they have to say about ignition condensers etc.

Hth,

Al.

Hi Al
Also very interesting as usual. I did inspect the number of coils visually by putting the springs side by side but stopped short of the realms of laboratory tests. I have now found distributors stamped with 8 and 10 degree advances. The Haynes manual says 11 degrees for the 650 engine and both 500 and 126 manuals show a plus or minus 2 degree tolerance as being acceptable on the advance.
So I am happy with something that looks and feels right especially as the engine is such an old basic design but I think that is interesting to note the possible variations and problems that can occur. I also found that two of the advance mechanisms had fallen apart at some time and been subject to “back street” repairs so that advance mechanism is worth inspecting when you have the distributor out.

I am also quite partial to a distributor and the best one I've used is probably standard for the 594 and 652 engine, but I'm not sure. it's marked S152A. It also has 201-R1-P1-4K.

fiat500 said:

I am also quite partial to a distributor and the best one I've used is probably standard for the 594 and 652 engine, but I'm not sure. it's marked S152A. It also has 201-R1-P1-4K.

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I'm a fan of keeping things simple and for me the 'Zelmot' distributor as fitted to the 126 (87 on) is as straightforward as it gets - even if the system is 'Lost Spark' with the twin dry coil and a ballast I've NEVER had a problem - just set the points and leave it alone, no HT cap and rotor arm to fiddle with
Ian.

Bleeding Knuckles said:

I'm a fan of keeping things simple and for me the 'Zelmot' distributor as fitted to the 126 (87 on) is as straightforward as it gets - even if the system is 'Lost Spark' with the twin dry coil and a ballast I've NEVER had a problem - just set the points and leave it alone, no HT cap and rotor arm to fiddle with
Ian.

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I've neve had that system Ian. If my distributor has the same markings as yours, mine must have been converted as it's a minute's work to change it back to a standard distributor.

As a nerd I'll dig out a couple more distributors and look at the markings.

fiat500 said:

I am also quite partial to a distributor and the best one I've used is probably standard for the 594 and 652 engine, but I'm not sure. it's marked S152A. It also has 201-R1-P1-4K.

Click to expand...

Had me checking the codes on a few and all have the S152 code, most with an A. A couple with the 201-R1-P1 code followed by a single number and a letter.
I tried to see if the codes related in any way to the amount of mechanical advance but no pattern.
Ian I have to agree with you about the rotorless ignition and I think I am right in saying that you can fit an accuspark electronic ignition allowing you to take the condenser out of the equation.

Toshi 975 said:

Had me checking the codes on a few and all have the S152 code, most with an A. A couple with the 201-R1-P1 code followed by a single number and a letter.

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I've got the same with a Zelmot one I looked at, S152....without the "A" suffix.
In Polish it says "under licence" to Magneti Marelli.

Then there's the older style distributor for the 499, which is an S76D and this one has 9 (degrees) stamped on it.

Bleeding Knuckles said:

I'm a fan of keeping things simple and for me the 'Zelmot' distributor as fitted to the 126 (87 on) is as straightforward as it gets - even if the system is 'Lost Spark' with the twin dry coil and a ballast I've NEVER had a problem - just set the points and leave it alone, no HT cap and rotor arm to fiddle with
Ian.

Click to expand...

Ditto