I have started to fit a “123” electronic distributor to my Lotus Elan. Very foolishly I did not read the fitting instructions properly before commencing, and simply removed the old distributor without noting the position of the ignition cable going to cylinder number one. I was then meant to turn the engine further until the Top Dead Centre (TDC) is indicated on the timing mark. The engine would then have been at the static timing point, at the end of the compression stroke for cylinder number one. But very foolishly none of this I did.
Thank you “h20hamelan” for your rapid reply.
I think I will try the “remove #1 plug, and insert long dowel or screwdriver (careful) also, your crank should indicate TDC” method that you suggest. Should the green light on the 123 distributor then be alight?
I don’t know. What does difference does it make, please? Did you ask in relation to my “Should the green light on the 123 distributor then be alight?” question?
looking through thr oil filler cap you should see both cams and their lobes, make sure that when you are seeing TDC on the front pulley, that both the cam lobes are pointing towards each other and tilting slightly downwards. This ensures you are at TDC on the firing stroke rather than being 180 degrees out.
Thank you Tony for your additional suggestion. When you say “when you are seeing TDC on the front pulley” I presume you meant “when you are seeing TDC on the front plug”? (If not, what did you mean, please?)
When the cam cover is in place and the oil filler cap removed only the exhaust cam is visible.
In the descriptions above, there are 3 different indicators of TDC on #1.
The notch in the pulley is aligned with the TDC mark on the front cover.
The #4 exhaust cam lobe will be facing (and slightly down) towards the inlet side of the engine.
Any object that you may have placed in the #1 cylinder will be extended as far up vertically as it can be before it starts to drop when #1 has gone beyond TDC.
All of these are ‘pretty close’ eyeball methods.
[edit] All 3 will be simultaneously present when #1 is at TDC of the compression stroke but you really only need the timing mark if the engine was running before you began the distributor change. Personally I’m a believer in using redundant methods.[end edit]
As an alternative to putting something down the #1 cylinder, there are several different kinds of inexpensive tools that indicate TDC w/ a reasonably high degree of accuracy.
There are a number of threads on this site about fitting 123 distributors. I would suggest having a search for them, particularly about appropriate advance curves.
When it comes to fitting the 123, there are two choices - set the 123 to TDC, then the advance entered into the app has to be total advance, that is static advance plus dynamic advance. This isn’t how the old mechanical distributor is set up, but has the advantage of ‘what you see is what you get’. This is my preferred approach.
The alternative is to set the 123 to the appropriate static advance (just as if it were a mechanical distributor) and then enter the dynamic advance into the app. Total advance is now the static value plus the advance indicated in the app.
The engine doesn’t care, all it sees is total advance.
This is how i set my 123 up on my rover v8. I used the distributor to set the static so i could move it without moving the distributor. I set the car at tdc compression on number one and the rotated the distributor so that the led just changed state and bolted it down. According to my timing light this meant that what the electronic advance through the app matched the advance shown on the crank.
If you look at the front pulley there is a notch in the outer edge of it (use some Snopake or similar in the groove to make it easier to find later). Do the same on the timing marks on the front timing cover. So if you now bring the engine up to TDC according to your marks, you can look into the oil filler hole to ensure the exhast cam is pointing slightly downwards and facing towards the other cam. This will ensure you are actually on the firing stroke and not 180 degrees out, giving you a base setting for the ignition timing. You then need to make sure that when you insert the distributor, that the rotor is facing the No 1 plug lead.
My apologies I said previously that you can see both cams down the oil filler hole, when in fact you can only see the exhaust cam ( my mind was obviously somewhere else when sitting at the keyboard)
I’ve recently installed and set mine up without issues so here goes with my experience.
Find your #1 tdc position on compression by whichever method you prefer. I went as far as using a dial indicator but not imperative. This will negate not having set it before you removed the old dizzy.
Install your new 123 in an orientation that best suits your rotor cap positioning. For me, all the lead outlets point towards the rear of the engine. Leave the clamping ring loose enough to be able to rotate the distributor for initial setup. I centered the bolt in the slot that screws into the block and tightened it down there. It allows some slight advance or retard to achive, for me, the 15deg @ 1000 rpm advance as recommended.
Once you’ve connected the blue and red wires, with ignition on, rotate the distributor body until you get the green led. Note the instructions about removing slack in the rotor arm etc. If you can’t see the led or have to rotate the body too far, you will have to remove the dizzy and rotate the shaft one tooth accordingly.
Where the rotor arm now points to is No1 plug. Essentially, you can set No1 to whichever position on the cap you like. Follow the firing order to connect remaining plugs.
Start engine, allow to warm up and then confirm you have the correct advance at recommended rpm. For me, 15deg @ 1000 rpm. Advance or retard distributor accordingly if you need to. Tighten clamp and you should be good to go. If you haven’t already done so, connect app to dizzy and enjoy the show.
Thank you all for all your very helpful replies. I have still failed to get my Elan to start - I’ve now spent 4 mornings trying to do so…
As I’m not certain to which plug the rotor arm is pointing, in addition to 1342, I’ve also tried 3421, 4213, and 2134. And in case (because of the direction of rotation of the rotor arm) 2431, 4312, 3124 and 1243. All without success. I am at a loss as to what to try next. All suggestions very welcome.
PS: I also was given an electronic Aldon distributor who had fitted it to his Elan. Unfortunately my friend has since passed away so I can’t ask him if he still has the mounting instructions.
There’s a sticker on the electronic module that reads “LOT#39 AJ-NV5M”. “LOT” as in Lotus?
Anyway if anyone has the instructions for mounting an electronic Aldon distributor that they could scan to this site (or to me via a PM), that would be very helpful.
Why don’t you just ring Aldon and get them to send their instructions, that way you know you have the correct information. They are in my experience a friendly bunch
I tried to send you a PM this morning (French time) but I’m not sure it worked. Please could you send me one - or else if you have it scan a copy of the Aldon instructions.
On Thursday (28/08/25) I sent Aldon an email which read as follows:-
“Hello
I have an oldish ALDON DISTRIBUTOR that has a little sticker on it that reads “LOT#39 AJ-NV5M”.
It has not been used for some years, but I am considering bringing it back into use as my LUMENITION suddenly stopped working, leaving me at the side of the road.
Please may I bother you to reply to the following questions:-
What does “LOT#39 AJ-NV5M” mean? (It was fitted to a Lotus Elan which is what I wish to fit it back onto).
I no longer have the fitting instructions - could you possibly email me them, please? Or failing that, post them to me (address below).
For future reference there are good installation instructions & general support here, including a video.
Not sure why you’re installing the Aldon distributor. Just set the engine at TDC on the firing stoke (as people have told you how to do) then install the 123 dizzy….
With the engine at TDC on the firing stroke the rotor should be pointing between 10 & 11 O’clock.
It is unlike them not to respond, but in the event you may be better giving them a cal, that will also enable you to ask anything relating to final set up as well, although in my experience it is pretty straighforward.
Are you sure it is an Aldon product as it may in fact be a Petronix unit from the number. Have a look at this site. It sounds like you may have an old Pertronix unit and the part number you show may have been updated to a new number, so send them an email and check out that part number before chasing Aldon.