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 - Electronic ing.

There are so many type of elec ing systems ranging in price from GBP50 to 200 can any body recommend a system for my 1977 roadster.
A Charman

I've always found Lumenition to be good. Either the cheaper Magnetronic or Optronic.

Make sure you have a good quality rotor arm.
Dave O'Neill 2

I've used the Lumenition Magnetronic unit on my GT for about ten years with great success. However I fitted to my roadster a unit which I purchased off E Bay from a chap Simon Lawther and the first unit did not work at all. The replacement worked but failed on the MOT ramp after about two months so really I have to call time on these units.
Iain MacKintosh

The Americans like the pertronix Ignitor and I see it is now available in this country. It's
Mike Howlett

The Pertronix Ignitor is a very simple, Hall effect ignition that is fairly bullet proof. The best thing about it in my estimation, is that it is completely reversible if the unit fails on the road - provided you have a second backing plate with pre adjusted points and condenser installed on it (since the only time I have ever been stranded at the side of the road was with a car that had electronic ignition on it that failed). Remember, when an electronic ignition fails, it is dead and the only way home is with a back up or a tow vehicle. Cheers - Dave
David DuBois

There is a large body of opinion, and some facts worth considering, in previous discussions of this subject contained in the archives. I have had three failures of electronic ignitions over the years, no failures of the points type system.

Regardless of what is done, the Lucas distributors were designed to have annual maintenance performed on them. At the very least, lubrication in the manner discussed in the factory workshop manual. In the area I live, dusty, removing the points plates, separating them, then cleaning and lubricating them, is a good idea. It, also, allows you to inspect the weights and their pivot arms for rust or dirt build up. These basic maintenance items are commonly overlooked when the electronic points replacement devices are installed.

I currently have a Petronix Ignitor system in a 77 International Scout II because the original, factory electronic ignition system kept failing in use.

Any original distributor is, most probably, in need of a rebuild by now--all that I have seen are. Whatever decision is made, make sure you have a good, sound platform to work with--a freshly rebuilt distributor which has been checked out to make sure it is giving the correct advance curve.

Les Bengtson

I have been running the Pertronix on my 72 roadster for three years and it has been very good and trouble free.
If you shop around it can be found much cheaper ordered direct from The USA but dispatched from the UK.
Trevor Harvey

Down here in Oz, many of the guys, including myself, have bitten the bullet and installed the 123 ign. This is a complete distributor assembly, with the only moving part being the shaft, all else is electronic. Fairly expensive at $A560, but when compared to having your dizzy rebuilt and recurved, the difference becomes minimal. I was recommended to use the generic British unit, 123 GB4 R, rather than the MG unit, as there is a better choice of curves which allows you to better match today's fuels.
Check out their website

Herb Adler

Don't bother, the benefits over a good condition distributor and correctly set-up points are marginal to non-existant. Many claims of how good they are result from comparing them with knackered original systems.
P Hunt

I bought a Sparkrite on Ebay for about 15, the car starts better. it's simple to put in, and if it does pack up, a switch turns it back to normal operation. I've had lumeniton before and I rate this as good as that.
c cummins

I bought my first MGB when I was 19. Last week I had my 49th birthday. Soon after buying that car I bought Mobelec Magnum electronic ignition. When I sold that car 18 years ago I kept the electronic ignition and fitted it to my "new" MGB. It is still in use. So electronic ignition can have a long and reliable life.

Tempted fate it will no doubt fail when I next go out!
David Witham

I fitted a 123 electronic distributor to my 1972 B a couple of years ago to replace my old distributor which was worn. The attraction of the 123 was the feature that allowed different advance curves to be selected as my car doesn't have its original engine. The car now starts more easily and runs better.

It cost 199 but probably now costs 250 due to the fall in the value of the versus the Euro.


Peter Burgess has started fitting 123 distributors to MGB and midget engines - see his web site. If he reckons it is worth doing, then that is good enough for me.
Mike Howlett

Do not overlook the Lucas/General Motors 45DM4 HEI system. I have been using one for over ten years with no failures.
Steve Rechter

The 45DM4 was standard fit for later North American spec MGB, replacing the very trouble-prone 45DE4 often under guarantee. The remote module is still available from the likes of Transpo, haven't seen a source for the trigger though, if you can't get a complete system out of a scrapped car.
Paul (too many Pauls own MGBs) Hunt

Worrying about what happens when the electronic ignition fails is silly. They never fail. The spare points you keep in the boot will rust away to nothing long before your electronic ignition fails. I've got an old Volvo where I installed a Crane aftermarket ignition in '91. Drove the car as my primary vehicle for a decade, stored it, left it in the rain, did everything I could to kill it, never ever had an issue. It still works, to this day. Your electronic ignition will outlive your car, and it will probably outlive you.

True, there's no performance to be gained over points - the electronic ignition will perform exactly like brand-new, perfectly tuned points, every day, until at long last your distributor wears out... and you move the same electronic ignition to a new distributor and keep using it... yup, nothing to be gained here.
Sam Good

"Worrying about what happens when the electronic ignition fails is silly. They never fail."

Rubbish, plenty of experiences of failure here and elsewhere. You may not, but then I've never had points or condenser fail in 40 years. Yes, I replace points every 10k or so, but I haven't had to adjust them between change intervals, and in any case I *like* working on my cars.
Paul Hunt 2010

I agree with Paul that electronic ignitions can and do fail. And they fail without notice.

There are plenty of reports of Pertronix ignitors failing on MG's and other vehicles. Also reports of other systems failures.

Even though my daily driver has the 45DM4 with the GM ignition module, I still carry a spare module with me.

Most failures with this GM system are either the ignition module was not installed with enough heat conductive grease under it or the dumb owner (DO) "tested" the unit without a proper load.

This GM unit will fail every time if the spark plugs wires are removed and the DO tries to start the motor while checking for spark by holding one of the disconnected spark plug wires in the vicinity of ground.

Steve Rechter

Hi Gents.
I have been using a Aldon Ignitor, its produced by a firm in the west midlands.
As soon as i put it on i noticed that the car started better, and actually ran better,plus slightly improved fuel consumption ( although no actual data to back that up ). I take the point that standard electronic ignition is "no better than a new set of points" but i noticed these improvements over the standard setup, and i use to change my points approx every 4-5000 miles and also check them in between.
IMHO i would choose electronic ignition over contact braker points every time.
Regards Neil.
Neil V J Reeves

For the past 18 months (14,000 miles)& in all weather conditions, I've been using an electronic ignition module bought from

Thus far it's performed every bit as well as the Pertronix (Aldon) Ignitor units I've used on my previous cars and at 20.99 it's cheap enough to carry a spare if you're really worried about reliability, they're easier to replace than points too. As these units require no alteration to the distributor it's cheap enough to experiment. I've seen these same units for sale at well known MG parts suppliers for more than double the direct price.

Electronic ignition is a well-worth upgrade in my humble opinion. It's an easy, cheap and reversible modification that really does give instant benefits & improvements without spoiling the character of the car.

I have a 1973 MGB GT which had been retrofitted with an electronic ignition by the PO when I bought it some 7 years ago. The EI finally gave up the ghost some 14 months ago and I decided to revert back to points and condensor on the grounds that if it packed up, I could do roadside repairs. Unfortunately, this became something of a regular event and I was forever having problems. Having had points and condensor setups in a previous MGB and Morris Minor and never having had problems I was at a loss to explain why I was having difficulties and have put it down to poor quality foreign replacements. Three weeks ago it did it again and that was that! I purchased an electronic points replacement similar to the one described by Mike for 25 and it worked first time with no change to the timing. So far it has worked flawlessly with the engine running smoother than it has for some time! 'Early days' I hear the purists cry. Fair enough and I agree. But so far so good and I keep a spare set of new points and condensor in case. However, if this new system works out I will buy a spare one and keep it in the glove compartment. It's a hell of a lot easier to replace than points etc when its chucking down with rain and blowing a gale believe me! Also as an aside, make sure you keep spare points and condensor screws - I dropped the condensor screw while trying to change the points in the rain and couldn't find it - luckily I'd had the foresight to keep a spare! Phew!
PJ Eades

Mike and Paul, that is the very unit that failed with me on the MOT ramp and was the second one supplied as the first did not work at all. I'm afraid that I have no faith in these at all and have reverted to points in my roadster.
Iain MacKintosh

Iain - I noted your comment on that previously hence my keeping a spare set of points at hand. As a matter of interest did you have the blue or red version as I recall comments some while ago about the earlier blue version causing some problems. This one is made by 'Accuspark' and I bought it off E-Bay from Watford Classic Cars. It also has a fairly thick aluminium baseplate, which I had to cover on the bottom with silicon paste (presumably to help it dissapate heat more efficiently). In any event I will report any significant changes. All I can say at the moment is it seems to be working very well and is a significant improvement on my former arrangement. Time will tell!
PJ Eades

Paul, I think that mine were blue (now in the bin) but it was only last Ocvtober that they were supplied so they were not very old and should have been of the latest type.

Good luck with it.

Iain MacKintosh

New distributors are available very cheaply now - not worth paying for a reconditioned one.

Aldon Ignitors are the same as the Petronix and are my preferred electronic ignition.

Electronic ignition does have an advantage over new points beside the no wear and no resistance benefits, the engine will idle more smoothly in my experience.

I would never spend the money on a 123 - spend it on head mods instead!
Chris at Octarine Services

Agree entirely but my GT has run for ten years on Lumenition Magnetronic ignition which I recon is very similar to the Pertronics. I must say that the idle is very smooth and that stsrting is particulary sharp.
Iain MacKintosh

All the "new" distributors that I've seen recently have no country of origin stamped on their housings. This alone makes me wonder about their quality. I purchased one several years ago from Moss and it wore out its bushings in less that 2 thousand miles! A re-conditioned unit, in my opinion, is a much safer bet as it can be tailored to suit your engine, available fuels and driving style.It can also be equipped with an electronic pickup, if so desired. I've been running a DUI GM based HEI system on my '67 supercharged engine, controlled by an MSD Boost Timing Master, for 6 years now and have been very pleased with the performance and reliability. RAY
rjm RAY

"no resistance benefits"

Have you measured the resistance of both? It's been claimed before the electronic ignition offers zero resistance, but it isn't true. Electronic devices exhibit a forward bias volt drop that is a lot more than points resistance. Hall-effect devices drop either 1.5v or 0.4v depending on whether they are sourcing or sinking the current. The original Opus electronic system used on the MGB dropped 1v, which is why the coils were changed from 6v to 5v. An electronic trigger of the Aldon/Pertronix type I have also gives 1v. An old set of points gave 0.5v, and a new set on-car gave a surprisingly high (to me) 0.4v when measured from coil terminal to distributor body. However when I started breaking this down only 0.08v was due to the points themselves, the biggest single amount was 0.2v in the coil to points wire, which under-cap triggers like Aldon/Pertronix have as well.
Paul Hunt 2010

To PJ Eades (Paul),

Your points/condenser problem may be related to the coil that you are using.

If you are using the coil that was installed with the previously installed electronic ignition, its primary resistance may be too low allowing high current to flow through the mechanical points. This would lead to early failure of the points.

A reasonable primary resistance would be in the neighborhood of 3.0 ohms.
Steve Rechter


There's a lot of difference between the old Blue electronic ignition units (no longer sold) and the new Red units. I too tried the blue unit which I bought for all of 7! It worked well when cold but the car would start misfiring when it became hot, curiously I noticed that this misfiring would all but disappear if extra loading was placed on the electrical system e.g. if I turned on the headlights. The red unit performs faultlessly and at just 21 I could regard it as a service item and replace it annually if I was concerned about reliability or longevity.

Good luck with the points, I will never return to using them, they are too much hassle. I use my MGB daily and I need it to be reliable.

Electronic ignitions do fail, we had 2 Pertronix fail within a couple of weeks and I wouldn't risk another. When they fail they do so completely, whereas points will generally give plenty of warning that they are on the way out.
Whichever system you fit will not give optimum results if the dissy mechanical advance system is not working properly.
Most of the recon dissies sold today do not have the correct springs fitted'and I believe new ones are probably worse, as no-one really knows what the original spec was and most cars now have different requirements for fuel and tuning compared to the 60's and 70's.
More power is lost thru inefficient advance than can ever be made up by electronic ignitions, it may start better and tickover smoothly, but is it running efficiently between 2000 and 3000 rpm?

G Cherry

I've not had an electronic ignition unit fail in ten years of driving an MGB daily and covering in excess of 100,000 miles. You only have to search the archives of this board to see how many instances there are of points/condenser problems and failures.

If I had two electronic units, especially one's from the well-proven Pertronix, I would be looking at other causes rather than the units themselves. I've always found Pertronix units to be of excellent quality.

Whilst a worn shaft/bearing on a distributor will have an impact on engine efficiency, this impact will be less pronounced with an electonic unit than with a points system where the dwell-angle will vary. Having more moving parts can only make things worse. Don't forget points will start to move away from initial setting from the moment they are fitted due to wear even on an otherwise perfect distributor, the non-contact trigger & receiver of the electronic unit will not affected by wear. The only fear with electronic units is total failure which in my experience is unlikely, even then a roadside replacement would be far easier then a points replacement.

There are many reasons why contact-breaker points have long-since been obsolete on new car production.

My car is solid state in iginiton, fuel pump and flasher unit. Contact points, no matter where they're fitted, cause too many problems.

Mike I agree, that electronics especially in new cars are extremely reliable, the voltage and current control is far more sophisticated. At the time of the Pertronix failure I suspected voltage spikes from the Dynamo, but was told by the manufacturer that the unit was protected from such and that it was just a faulty batch. Since we were rallying the car we couldn't afford 2 minutes at the side of the road let alone 15 to change the dissy, so points it is and although we've had a few coughs and splutters in 14 years, we've always made it to Service.

G Cherry

I have had a Luminition Optronic on my 72 Roadster since 1989 and it is still going strong. Nothing has failed. The distribuitor now needs replacing as it is showing signs of wear.
Richard Thompson

I personally prefer the Lucas CEI having found that it is really a GM 4pin HEI system. I upgraded a CEI with the Pertronix D2000 4pin HEI Module and used the matching Pertronix coil. In the cross flow headed 3main 1800 that's in my ZA Magnette, the engine fires up quickly and with no missing even under load at high RPM.
John Perkins

The CEI was what North American spec cars ended up with in the 45DM4. I've never heard of one failing, and the output modules are still available, not sure about the trigger in the distributor though.
Paul Hunt 2010

I'm on my 3rd electronic ign. A Pirhana gave 3 years. A Jolley Engineering (Classicheads) 2 years and I'm now on a Boyer Bransden which is a transistor assisted so still has points. I've kept +ve earth which has restricted my choice.
The B-B is really a classic motor cycle unit, but will give all the sparks a B series needs. Being assisted its easy to take it out of circuit if it fails and the capacitor is not needed but I left it bolted in where its available for emergency use. I'm sure my car starts and runs better with the fatter spark
Stan Best

Just to let you guys know that you can pick the electronic ignition kits up from and you can even get the powermax kit with red rotor arm for the price of the Accu kit.
S Lawther

By way of an update on my previous notes on this subject. I fitted an electronic points system similar to the one described by S Lawther two months ago following a series of points related problems and it has performed flawlessly, with the engine running noticeably smoother than previously. All for the princely sum of 25. I'd say that was fair value for money given the results so far!
PJ Eades

Only problem is that this is the system that I fitted as well and had two failures in short order. I've now given up on these.
Iain MacKintosh

This thread was discussed between 02/03/2010 and 13/05/2010

MG MGB Technical index

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