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123 Ignition to Replace Bosch VJ4 BR35 in Giulia Sprint Speciale

2804 Views 13 Replies 8 Participants Last post by  ar101.23
Does anyone have experience running a 123 Ignition in a Giulia Sprint Speciale to replace a Bosch VJ4 BR35? I am trying to understand which specific model of 123 I should consider and whether one of their pre-programmed ignition curves will fit this specific application. The Alfa 4-R model would seem to be the correct model and it has 16 pre-programmed curves but none of them are specific to this application. Any help / guidance is appreciated. Thx.
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On one hand, it is hard to answer this question in the absence of a published diagram of the VJ4 BR35 advance curve. The Giulia Sprint Speciale/Spider Veloce were about the most highly tuned Alfas from that period. To get an abolutely identical curve, you would have to take your distributor to a shop that still has an ancient distributor test bench and have them plot the curve. Then you would purchase the programmable 123 and input the curve as measured.

On the other hand, these vintage distributors were all set for octane ratings that are no longer available. Since many of the pre-programmed curves are intended for Alfa twin cams with twin Webers, and the curves were not wildly different to start with, I believe the 4-R could be set to work decently on your car.

Why do you want to replace it?

If you do, make sure you match it with a lower primary resistance coil to fully benefit from the electronic triggering. This will allow you to increase spark energy, along with an increased plug gap. Aim for a 1.5 - 2 ohm primary resistance such as the Bosch "Red " coil.
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Here's the Bosch JF4 curve from the old Shankle catalog.As I understand it,same curve as the VJU BR35


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Thanks - is the JF4 curve the same as / similar to the VJ4 curve? I had thought the VJ4 was specific to the SS. Am thinking maybe I should just go for the fully programmable 123 for maximum flexibility. My reason for looking into the 123 in the first place is that I discovered that the the springs on my advance are broken and I am getting some pinging at lower RPMs - my plan is to have the VJ4 sent out to be rebuilt but I am in the process of sorting the car for reliability (it is relatively new to me) and don’t want that work to come to a standstill while I wait for the distributor - plus I have had good experience w fully electronic ignition in my Allard and would like to see how it works in the SS.
I'd suggest getting the fully programmable bluetooth one, it's not much more expensive. Buy once, cry once.

You can easily program & change curves, and do stuff like change static advance without having to rotate the distributor. It also lets you livestream data to your phone and even lock the car via a code.

See post #505 in the thread below, I've got a video of the output from my GTV and examples of the curves I'm using:

How many miles do drive per year your Spriont Speciale ?
If it is a limited amount of miles I would not consider a 123Ignition. Unless you present distributor has broken down and you need a new any how.

Otherwise buy a simple upgrade for a standard distributor; contactless points; such as ; AccuSpark Electronic Ignition
This a good solution and very easy to install. No more worn points and smoother pick up of the engine.

( I had a 123Ignition in my Berlina 2000, removed it again after many trial and error issues concerning low rev running).
I drive my cars quite frequently and the car will likely be used for the occasional 1,000 mile tour once dialed in. One of the first things I did when the car arrived was to swap out the points for a Pertronix - could not agree more that this is the way to go with a standard distributor.
Hi all,

For speaking in original 'distributors' terms, I feel that I need to add some " counterweight " in this thread. Not for starting again a discussion that has already taken place, but to testify that originality can and should have a place, especially on this nice forum.

My car, a late 101 Giulietta Ti, is stored in my garage for 3 years unfortunately, waiting for a needed 'cosmetic' body repair.
I have driven that car, on regular base, winter and summer, for more than 15.000 km over a timespan of several years now, with the original Marelli S71b distributor.
Except of two 'ten minutes jobs' of cleaning the contact points in the car after a longer time of inactivity ( just scraping of the oxidation layer on the points with a small putty knife), the engine started and runned always perfectly, wathever traject I made. ( short or long trips, snow trips, climbing mountains, classic circuit race ...)

Why would I change my classic car with a non authentic modern electronic device, when it is in fact running so well and is a demonstration of how good, reliable and most of all 'ingenious' the existing systems were yet in the sixties? And yes, 3 years ago we already had the modern fuel composition on the gas stations.
I'm not going to contest that there are of course all kind of advantages with these modern devices, that's not the point, but I'm only trying to make a plea for preserving the more than 50 years old technics from disappearing.

How many people would enthusiastically say " WAUW" when finding out that an Alfa 2500 6C has a computerised distributor under the bonnet ? Even when it was camouflaged ? ... at least I would not .

Just a thought, my thought ...

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Of course, but that’s an old can of worms that always comes to the apex of arguments that at what point does something now available that can make your classic car more reliable make it not worthy of what it left with from the factory?

I have points in my rebuilt distributor on this Spider. I’ve had a pertronix distributor on my other cars and they worked great too, but only at a concours will anyone really notice, and even then, big deal. If you’re driving several hundred miles away from your home and your distributor or any other thing on your car leaves you stranded because you were hardheaded enough to just go with what it was made with, it really isn’t any “better” except in your own mind. At what point do you realize there are a lot of things you put on your car in a restoration that aren’t exactly what it was like from the factory, hidden or not? Like an electric fuel pump for instance. The bracket is right there on my chassis, but it didn’t come stock because it’s a Normale. I haven’t put a Bendix in yet in case my Fispa fuel pump craps out on me, so I’ll tell you someday if I was either hardheaded, or just didn’t feel like putting one in after I was either stranded or it didn’t start!

I say things that are easily remedied for someone who eventually wants it changed back to stock, is not a big deal. Even during a concour, batteries and tires apparently are given a pass that weren’t original. And those a super visible. There are so many nits to pick on the road to non-original versus stock, it’s truly exhausting. No offense meant...perhaps my “point” has too much oxidation on it!
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Hi reffiesj,

I just realize that I have 'hacked' your thread, I shouldn't have done that.
it was just a spontaneous reaction of me and I apologize for this.
I hope you get more adequate replies on your request than mine.

Dave, most likely there will be other, more appropriate, occasions to exchange our thoughts in this matter, although that what I had to say has been said yet. So I'm sorry to you too.


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No worries at all Thierry! The originality conversation is a true Möbius strip...
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I beg to differ on the issue of electronic being synonymous with more reliable.

Most of our cars (the pre-1979 ones) have been driven well over 100,000 km with points ignition. Were they reliable? Yes, as long as the system was not neglected. Points do erode and need to be cleaned and eventually replaced, as well as the rotor and cap.

Electronic ignition was first introduced on high performance machines that needed more spark energy to function correctly - for example the 2 liter 911S or L71 427 Corvette. Points can only switch so much current without eroding too fast. Having the points signal the spark timing to an electronic circuit allowed more powerful sparks. This was the Capacitive Discharge or CD system.

The next step was to replace the points with electronic switches (inductive Hall effect and optical have been used). This gave a more consistent spark timing as it eliminated the need to clean, replace and adjust the points. Emission controls might have been the motive behind its advent (GM made electronic ignition standard in its 1973 model range). The distributor still included mechanical and often vacuum devices to provide the right advance in various conditions.

A bit later, engine management systems such as Bosch Motronic took over the spark advance functions, not depending on mechanisms inside the distributor anymore but instead relying on a microcomputer to numerically establish the proper advance. No more mechanisms to wear out, and the flexibility to input more variables such as knock sensors. Numerical advance was never easily retrofitted to an older engine - until 123 arrived a bit over 10 years ago.

What you gain with 123 is timing accuracy and the flexibility to switch from one curve to another. You also gain immunity from mechanical wear in an advance mechanism over 100,000 miles or more... but who of us needs that?

Are electronic ignition conversions reliable? Most are, although there is some crap out there, bu none of it is aimed at Alfa enthusiast. Are they more reliable than points ignition? This depends on how you maintain your points ignition. To me, the real question is: what happens if something fails in your ignition system? If you have an electronic ignition conversion and no tools nor access to spare parts, you're screwed. With a 123, you need another distributor. With a Pertronix or similar device, you could always carry a set of points in the glove box.

I had a 123 on my car and I sold it. It never failed or gave any signal that it would. What did it was the Derale electronic fan controller I was using for my cooling fan. It failed when I was stuck in traffic. Got me thinking. Old electronics are fussy. The same year I had a GTV6... can you spell "poor connections"? When you depend on multiple senders to run your engine, a bad contact on a single connection can spoil your day. I decided to go back to stuff I can fix by the side of the road with the small tool box/parts reserve I keep in the trunk. So I went back the the original Marelli distributor and added a vintage Delta CD system. Because it has an on/off switch. Yes, I'm a bit crazy. And believe me, I don't give a **** about total originality.
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BTW reffiesj you are in sort of a dead end. No, you can't assume the VJ4 BR35 curve is the same as that from a later distributor. To properly program a 123, you would need to get the curve from your VJ4 measured... but it is broken.

It might be worth mentioning that the 16 pre-programmed curves (some of which are duplicates) supplied with the basic 123 are almost integrally the same ones you can find in the back of an old Shankle/Alfa Ricambi catalog, including the one for the "Special Sports" recurved distributor that Shankle was selling way back then. And perhaps this is because somebody supplied Aryan Schutz, the 123 creator, with those curves to persuade him to develop a 123 for Alfa applications.
I put a bluetooth programmable 123 in my spider last December and love it. My Bosch was shot with the dog gear flopping on the end of the shaft. I am going to rebuild it and have a spare. The 123, is a toy. It is loads of fun looking at the data it produces. I learned my tach is off and it has a speedo function to use while I am fixing my old one. There are loads of centrifugal and Map curves out there that serve as a starting point then look at your advance and vacuum and customize to your heart content. Just my opinion, I could be wrong....
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