Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Advise for spare dizzy in 80 LE

I am thinking of obtaining a spare distributor to carry along in my 80 LE. The question is can you easily use a regular points type distributor in an 80 MGB that has the stock electronic ingnition?

I understand that if the electronic ignition should go south, which can happen without any notice, you are virtually out of luck. I would like to be able to simply replace the distributor with a spare points type and thereby cut out the need of repairing the electronic ignition on the road in order to get home.

Is this possible? What is entailed in making such a switch? Are there certain lucas distributors which would be better for a slightly built up 1800 with dual SU conversion? I would need a vaccum advance type distributor for sure.

Any advice?

My '80 LE has 80K miles on it. The electronic ignition has never failed...had a bad rotor once, '64, with points type distributor failed several times. I think you're heading in the wrong direction here. Seems to me the electronic system is pretty reliable.
R. L Carleen

If you really want some extra power and reliability, go the Brit-Tec website and order a euro distributor system with a pertronix ignitor.
GM Chohaney


I understand your pain. The factory EI went south on my 78 MGB, leaving me stranded until it cooled down....usually 10 or 15 minutes. This happened several times....I replaced the EI dizzy with a Lucas points distributor...(#41527?) I now carry a set of new points,condensor, and rotor, as well as a complete distributor ready to go in both my MGB and my MGC.

The points dizzy have never left me stranded and helpless as the EI unit did. A quick change of the points, re-gap of the points, or a new rotor always got me back on the road!

See you on Saturday.

rick ingram

Exchanging a more for a less reliable system just tells me that you don't
understand the technology. It's really not all that complicated. Read and learn. You'll never get stranded if you understand what you're dealing with. Electronic ignition systems are NOT some arcane unintelligible bit of voodooo.
R. L Carleen

I doubt Rick doesn't understand the dizzy types, I personally prefer the points style as well. Points are asily adjusted, easily changed and relatively inexpensive. No optical trigger or amplifier to fry and be unrepairable.

Rich, a points dizzy will work fine in your system, all you need is one of those distributors, and get one with a vac advance instead of a vac retard unit, then run a wire from the external spade on the dizzy to the neg side of the coil. The rest from the cap to the sparkers is the same. Good luck, let me know if you need one.


Rich. The Euro-Spec distributor, if any are still available, is not a bad way to go. A good rebuilt Lucas 25D or 45D points type dizzy is also good, but make sure the rebuild has been done by someone like John Twist who can turn out a decent rebuilt. Most available are of poor quality.

Up until 1980, the standard "electronic ignition" was the Lucas 45DE4 or Opus system. This was not very reliable and mine went out in the first three months of ownership. The 1980 models used the Lucas 45DM4 Constant Energy system which was significantly more reliable.

As to which system is more reliable, I do not know. Well made examples of both are completely reliable for long periods of time. One thing to consider, however, is that the distributor actually consists of three parts working together. The triggering device (points, light beam or magnetic pick up), the mechanical advance and the vacuum advance. The points and condensor have to be replace about every year. The vacuum advance should be checked for funtion annually. The mechanical advance should be taken apart, cleaned and lubricated annually. With a points type distributor, this becomes a regular part of the annual points replacement. With the electronic triggers, this preventative maintenance is often neglected. The only test I have seen, sent to me by Bob M., showed there was no difference in engine performance between using the points type system and an electronic ignition when both are in as new condition.

When there is an ignition failure, as there always will be over the years, a points type distributor is easier to troubleshoot than an electronic ignition system. Nothing made by man will work forever, but some things made by man are easier to fix than other things made by man. Les
Les Bengtson

RL - I have a complete understanding of Hall effect sensors and circuits, which is why I knew exactly what happened that left me stranded in the middle of nowhere a number of years ago. It also left me with no way to move the car untill things cooled down enough for the Hall effect to start working again (car was operating at normal temperature, also not an MG). After several hours of going about 10 miles and then letting the engine compartment cool, then getting another 10 miles, I made it to a phone to call in the calvery. On the other hand, I have always been able to limp a point type ingnition home when it failed.

Regardless of that, I did put the Pertronix, Hall effect ignition in our MGB. I also have a spare backing plate with preset points in my box of spares so I can get home if the electronics fail. After having worked with electronics for 39 years (fixing failed systems), I don't believe that it is here to stay ; ). Ask Les what he thinks of electronic hard drives right now.
Cheers - Dave
David DuBois

re: On the other hand, I have always been able to limp a point type ignition home when it failed.

Thank you! This was my "point", exactly!

rick ingram
rick ingram

Thanks for all the information. My concern is that I am begining to plan for some extensive summer trips in my MGB. Last summer we drove my 57 MGA from St. Louis to Oregon. I like the secondary roads and found myself in some really remote areas even without cell phone access. In the A I was fairly certain, baring a large failure, that I could fix about anything with the extensive spares that I carried.

This summer I plan to take the MGB to New Jersey again traveling on secondary roads wherever possible. I have begun to plan what maintenance I want to carry out before departure and what spares I want to take. The electronic ignition currently in the car will remain. It is working quite well. However I am concerned that if it would stop suddenly I could be stranded in a remote area with no way to get on the road again.

Therefore I am interested in finding a possible "plan B" backup that I can easily carry with me. As long as I can easily install a regular points distributor, hooking up to the coil, without having to worry about taking out the existing electronic ignition, I think the planning part of my problem is solved. Now I need to go find a suitable spare distributor for backup duty.


Rich, I found a place that sells MG distributors a couple of days ago while searching for something else. Their prices are reasonable. I have never tried their products and I'm not sure if the 66-74 unit has a vacuum advance. The advance isn't necessary to get you going. Their 66-74 unit is a one size fits all (it appears the euro spec distributor is also a one size fits all) so it may not have an ideal advance curve for your car. It would get you going if your electronic distributor fails.

I also noticed Philbin can recurve your distributor and install housing bushings.

For someone looking for an MGB electronic distributor curved for your engine see;
I have not tried their product. If you order a distributor from them they have you answer lots of questions about your engine and they curve the distributor for your engine. Their ad is in the current issue of Classic Motorsports Magazine. BTW the current issue also has a 10 page article on the MGB.

Clifton Gordon

There isn't a choice between vacuum advance and retard, they are all the same. The difference is in how they are connected - whether to the carbs or inlet manifold - they both advance the timing, and you set the timing for both with the vacuum disconnected. Carb applies no vaccum at idle and hence no advance, then rapidly increasing vacuum and hence advance as the throttle is first opened, and gradually reducing vacuum and advance as it is opened further. Inlet manifold vacuum applies maximum advance at idle, and gradually reducing advance as the throttle is opened. UK cars used the same engine and distributor when the take-off was moved from carb to manifold, which is simply a device to reduce exhuast emissions at idle.

I see little point in carrying a petronix-fitted distributor around in the car as a spare, you will never know if it works or not, and like any electronic system they can go phut without warning and then you are stuffed. By contrast there is little in points to go wrong, it will not go 'out' in the boot (and in any case is simple to readjust at the roadside). The points may need a quick clean if unused for some time, and you will need to be able to reset the timing.
Paul Hunt

This thread was discussed between 16/03/2004 and 18/03/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.