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MG MGB Technical - electronic ignition

hello all, i have been busy balancing and generally fiddling with carburettors. however i have come to the conclusion that my general running issues maybe down to a worn out distributor - possibly the vehicles original.

i wish to upgrade to an electronic ignition system for ease of mantainence.

i've seen all sorts of kit from pirhana to the ford module being developed by chris@octarine.

basically i'm looking for some advice on what systems are best etc.

cheers for any input.
d buck

I spent a fair amount of time researching the same topic for my 78 rubbernose running with twin SUs. I chose the Lumenition Magnetron for simple installation and the fact it fits inside the existing distributor thus keeping the "original" look of the engine bay. Also it is easily reversable, so at a pinch you could put your old points and condensor back inside the distributor if the electronic system fails.
From what I've been told, failure is something almost never heard of in the simple Magnetron system. You're more likely to get failure in a complicated system where reverting back to original isn't an easy option.
The Magnetron does rely on the existing distributor being in good mechanical condition. That is you need the spinning mechanism to be problem free. All you're replacing is the mechanical points and condensor. In that respect some might argue if there is any benefit at all. For my own case I used to find the timing was out and needed adjusting every 3 months when I did my regular service. Since fitting the Magnetron more than 2 years ago I've not had to adjust the timing at all.
D O'Brien

If the distributor really is worn out then fitting electronic ignition is only getting round a small part of the problem. If you had a good distributor (and no other defects) I'm sure you wouldn't have any running problems. I've never had a set of points or condenser fail in over 30 years, and since I started checking dwell instead of gap they don't need adjusting between replacement intervals either. The problem with electronic stuff is that when it fails it usually does so without warning, totally, and can only be diagnosed by substitution. By contrast points usually give you fair warning, are easy to diagnose, and relatively quick and easy to replace at the roadside with minimal tools. There are many people here and elsewhere who even though they have converted to electronic trigger or full ignition still carry points and condenser ... and have done a practice fit so they can do it at the roadside. I have heard of some systems that require you to bodge the points plate such that points and condenser cannot be retrofitted.
Paul Hunt 2

I'm very much with Paul on this for Lumenition type set-ups. I ran with a Lumenition system for a few years and thought it was fine until it developed an intermittent fault that left me well and truly baffled and stranded. I reverted to points initially as the only way of diagnosing the failure. I stayed with them as I couldn't discern any performance difference and I can diagnose and fix any wear or problems in seconds.

However, the Ford module Chris Betson is investigating is a fully programmable EDIS ignition which takes things on from simply replacing the points and would give more tuning flexibility for modified cars - nothing that can't be done by clockwork but much, much easier on a laptop.
Steve Postins

If the B had been fitted with the kind of dizzi which allows one to adjust the dwell with the engine running, I would have stayed with points - as it happens, I moved on to Lumenition in the 80s - and the units have proved quite reliable when mounted in a cool spot. However they are expensive and you do need to carry a spare !

An electronic set of points is pretty much the same no matter what brand. They all seem to be quite reliable.

Some of those that have an outside box have a heavier duty transistor doing the switching so that you can go to a higher voltage/amperage coil.

If you go to a wider gap plug you will be forcing the system to draw more juice and produce a higher voltage to get the spark to jump the greater distance. Likewise if you go to a higher compression or supercharging, you will find that it takes more volts and amps to jump the gap. Compressed air acts as an insulator and increases the resistance to a spark jumping the gap.

I've used some form of electronic ignition in all my cars since the mid 1970's. I've had one electronic failure in that time.

As indicated by the prior posts, electronics won't correct problems in the advance system or timing, or in bad distributor caps, wires, etc. It will assist with the coil rising to a higher voltage to produce a spark where the stock system can't reach that level because of less dwell time. In most cases with a stock system, converting to electronic is an issue of improved reliability and less maintenance.
Barry Parkinson

The EDIS system is ideal for modified cars, but will also work really well on a standard car. It can be mapped to get the best out of the car on the laptop, where as a dizzy relies on weights that can be changed, but seem to be a black art! Matt Kimmins is now selling complete kits in the UK, and with Chris is starting to look at a shop fitted solution (if you are not a DIYer). The total cost is less than some of the EI options out there, and it completely curcumevents any dizzy problems as you no longer need the dizzy! There is a failsafe setting that will allow you to get home with timing at 10 deg BTDC, or if you leave the dizzy and coil in position you can reconnect the old system in about 2 minutes! The main draw back is the complete lack of originality! If you want the car to look standard under the bonnet than it's not for you. If you want a modern solution then it looks good. If I get any problems with my dizzy I'll definetly go down that route. Info at

I D Cameron

i use my car everyday, and i have all but eliminated my running issues. however the distributor is worn and i could risk spending more money on a new one or buy an electronic kit and have piece of mind.

i really like the sound of kimmins setup, i am in the process of investigation though....

in terms of originality i am not too bothered, my car is original but i am not too concerned with keeping it that way as it's my daily driver and i need reliability.
d buck

D. Please go back and read, carefully, what has been written. I wrote an article on this subject for my website and this has been covered a great deal in the past. Hence, the archives provide a wealth of information on this subject.

Your post, "However the distributor is worn and I could risk spending more money on a new one or buy an electronic kit and have piece (sic) of mind." What everyone has been telling you is that:

a. There is no such thing as complete peace of mind. It is all relative and both points and the electronic points replacement systems can fail. Therefore, for peace of mind, you need to install the electronic points replacement system in a points type distributor and carry a spare set of points with you.

b. For either the electronic points replacement systems, or points, the basis of the system is a new or properly rebuilt distributor with the proper mechanical and vacuum advance curves for your engine. The electronic systems will hide some of the problems with a distributor better than points will. It will not hide all of the problems of a worn/malfunctioning distributor, nor will it hide some problems forever. (It will hide an improperly ground points cam forever--the cam is now just a mounting piece for part of the electronic system. It will hide a bent dizzy shaft or worn bushing for a period of time. It will not hide a malfunctioning advance system.)

c. An electronic points replacement system, on a distributor in good working condition, is a direct replacement for a set of worn out points. So is a set of new points.

d. There is no magic cure available and both the points and the points replacement systems require regular (annual) distributor maintenance if the systems are to continue working reliably.

"Peace of mind" is a relative thing. If installing an electronic points replacement system into and old worn distributor will give you peace of mind, you are still learning. Enjoy it while you can. Anything can, and will, break. All you can do is maintain the vehicle, use systems in good condition and keep them that way, and carry some common spare parts.

Les Bengtson

Hi all.

I still think that the ultimate answer (in the UK, at least) is to track down an old Sparkrite unit, which :

Reduces the load on the points.

Provides strong capacitive discharge sparks.

Can be switched back to standard points in moments.

Looks 'right' on later cars, because it is !.


I have just finished fitting one of Matt's EDIS kits and I must say I have been very impressed with the standard of the kit and also with the support I have rec'd from Matt. I haven't actually finished tidying up the wiring yet but it does run, and very nicely too, but it is a bit early to give you any feedback on the performance of the car with the new kit. I'm certainly looking forward to improved reliability (no more points !), bigger sparks, lower emissions and I can always change it back if I feel the need.

Andy Torode


There is not actually much on EDIS in the archives as it is a relatively new development for the B (there is of course plenty on the other options). But the EDIS pretty much addresses all your points!

a) If the EDIS fails it has a default mode that can get you home. Further to that if you keep the original kit you can switch back at the road side in 2 minutes or so. So you have 2 back ups.

b) EDIS completely replaces the dizzy. You can leave it in situ as back up or remove and cover with blanking plate.

c) No need to worry about points.

d) From what I have seen (and I've been in a couple of B's now with EDIS) it is the magic cure!! Albeit a very unoriginal one that won't suit everyone.

When/if I get to the point of wanting/needing to replace the dizzy I'll definetly go for EDIS. It gives you complete freedom to map the ignition to suit your driving and engine modifications. In the UK the kit is about 150 all in from Matt, so it is not a highly expensive option.

I D Cameron

why can't the edis system get its timing signal from a locked down distributor with a transistor switch. You wouldn't need that weird front wheel on the crank pulley?
Barry Parkinson

My reading around the subject suggests it can, with the simple solution being an optical type trigger as used in some points replacement systems. I'm toying with the idea of using the one from my defunct Lumenition. The crank wheel trigger would be more accurate though. I'm also wondering about the possibility of using a Manifold Air Pressure sensor in the vacuum advance line as oppposed to the throttle position sensor for the second variable after rpm. Any advice Andy, Iain?

In the meantime I'm also running the Sparkrite as my nod at electric trickery. It stops the points burning and ups the spark, but I find the points do need checking every few thousand miles as the plastic heel wears.
Steve Postins


Using the distibutor can be done I think. I assume that by locked down you mean that the mechanical advance etc is removed. I'd contact Matt to ask about that if I were you. The dizzy is connected to the cam, so will be spinning at a different rate to the crank, but I'd think the module could be programmed to adjust for this.

As for the pressure. I believe that the MGB manifold tends to have variable vacuum pressure due to the siamesed port design. There is something about it on Matt's website, but I think that is the principle reason for the TPS rather than vacuum sensor.

I D Cameron

I'm using megasquirt for spark and fuel on my 'B. The locked down dizzy works fine for triggering the spark, but it does wander a bit from slop between the cam and distributor drive gear. Triggering from the crank is more accurate, but I doubt it makes a huge difference in an unmodified engine.

There's no issue with using MAP to trigger the spark with siamese ports with a standard cam. Not sure about a more radical one, or with a DCOE and no balance tube - the timing might wander a bit at idle.
Mike Polan

You don't mention the year and how your B is setup (standard SUs, Weber aftermarket and other modifications to fuel and exhaust), but you're at the right site. One of the guys that posts on this site took an old DM2 MGA distributor that I had in my parts boxes for years and traded (with a little cash on my part) for a nicely rebuilt, recurved 25D with pertronix electronic ignition for my '80 LE. I haven't installed it yet, along with about a thousand dollars of other parts scattered around my shop just waiting for the time to get it done. I'm sure he'll see this thread at some point and reply.

What system is best will rely on the specifics of your car and how you intend to drive it. Sounds like you mostly want ease of maintenance. As noted, the carburetion, exhaust, ignition coil type and condition, general condition of the engine (age and compression type, etc.) should be considered to get you the right distributor.
Rick Penland

1969 engine in 1967 3syn car
5000 mile since rebuild
160 psi on each cylinder
bigger valve head
twin stock SUs with standard air filters
stock cam
uses a dab of oil [but nothing major]
stock N9Y plugs, but did run for a time with 12YC
recently rebuilt fuel upmp
carburettors balanced last weekend
lucas sport ignition coil
new plug leads
new distributor cap and rotor arm

so she's in pretty good condition.
d buck

Don - I still have such a Sparkrite system in the garage! I never bothered fitting it to anything I've owned since the late 70s as I never found any difference over a properly maintained and set-up points system.

I wonder how Chris's system compares to the 123 Distributor from Holland

I found this a few days ago when browsing then a couple of days later the latest issue of the MG Owners mag also featured it for MGBs amongst other things. Features multiple (16) curves referencing Lucas numbers, so should be able to select the correct one for your engine. However as even the original curve probably isn't ideal with today's very different fuels, and not least the plethora of North American curves over a relatively short period in an attenmpt to keep withing the emissions limits, it also gives quite a bit of scope for trying alternatives. Expensive at over 200, in my book.

I still reckon a knock-sensing retard system is the best ...
Paul Hunt 2

throw the dizzy away contact aldon for a new dizzy they allso sell a electronic ignition with three years on it about 130 pounds for the lot you cant go wrong


"It can be mapped to get the best out of the car on the laptop"

How does one go about mapping the system?


Larry Hallanger


Essentially you plug in a laptop and then can 3D map. That is, you can set the ignition advance dependant on both the revs and the throttle position (on Matts system, other set ups can use vacuum). A dizzy has an attempt at this by using vacuum advance, but it is a bit rough on the MGB and often performance dizzy's actually remove this and just use a 2D map where only the revs are taken into account. Of course if a car is at 3k rev cruising you will want different things to be happening with the timing compares to 3k revs with the throttle wide open. I suspect performance dizzy's are set so the best timing is achieved when you floor it!

With Matts system you can plug a laptop into the megalite unit and change the map, so you can actually sit in the passenger seat while someone else drives and alter the ignition timing on the move to work out the best settings! I think Matt is now working with Chris Betson to put together some default standard maps for a variety of systems. I have seen it installed on 1868cc engines both in an early B and a late B, with both SU and Weber carbs. More details from or ask on Chris Betson's forum which can be reached from

I D Cameron

Or go direct to

Chris at Octarine Services

I had a Pirhana on for about a year. It developed a high BMEP misfire and languishes on a shelf in the garage.
Stan Best

Mapping the curve is easy, compared to knowing what map to set it to!
Paul Hunt 2

Mike, I mailed Matt at kimmins about using the dizzy for the signal and he says it's no go with the electronics they are using. Can you elaborate on your set up? Is is EDIS based?
Steve Postins


I believe that Chris's forum answers your question of "knowing what map to set it to", specifically you need to set it up on a rolling road (dynamometer on this side of the pond) if you don't have an engine that is the same as one that is having a map developed for.

Larry Hallanger


I got close to buying a knock-sensing retard system (J&S Safeguard) but delved deeper and found comments to suggest that it had trouble "hearing" even with silky smooth Japanese engines - a good mechanic was getting better results tuning by ear. I image it would be deafened by a tappety old B, even if you did manage to mount the knock sensor, but it would be a great solution if someone can do it.
Steve Postins

Larry - exactly, that has always been the case, but that will be a very expensive and time-consuming job on a distributor with vacuum advance, which is one of the reasons why race-tuned engines don't have them. And if you are going to expend any money or effort on fancy distributors you need to do that even if you have a bog-standard engine, because the fuels are so different. Otherwise you might just as well use the original curve and run it with the maximum advance it will take without pinking at any combination of throttle opening, revs and load.

Steve - I came across this knock indicator ( see also and which is a lot cheaper especially if you get the microphone off a scrapped Montego. I didn't fancy spending all that dosh on the J&S with no information about the most important bit which *is* the microphone and its mounting. I reckon that if I could get the indicator to work, I could build the bits to get the output to drive the points plate in place of the vacuum capsule.
Paul Hunt 2


I am/was just ready to go over to J&S and buy their retard system since I just can't overcome my persistant pre-ignition knock (9:1, flowed head, 101BR2 Aldon dizzy, Piper 270 kit). I've got limited tuning skills. I'm also afraid of creating such a modified-monster that noone will know what to do with it! More specificly, what did you learn about the J&S, if anything? You can write me here or e-mail me. Thanks a lot.
Steve Meline

With any modified engine, and any standard engine on modern fuels, the only way to set timing (if it pinks at the factory setting on the latter) is to retard it bit by bit until it doesn't pink at any combination of throttle opening, revs and load. All engines differ, even factory-fresh ones. The factory timing figure takes this into account plus a safety factor, the result being that *some* engines can run more advance without pinking, and give you better performance *and* economy, that was certainly the case with my new BL car in the 70s. Whenever I got it back from a dealer service it ran like a dog (relatively) until I put it back to its ideal position again. It is also certainly the case that my roadster had a tendency to pink and runon at the factory setting even on 4-star leaded (99 octane), and much more so on unleaded, even Optimax 98. Tesco have now made a 99 octane available at some filling stations, haven't had an opportunity to try that yet.
Paul Hunt 2

I was looking at using it as a performance device, in the assumption it would give the perfect advance curve. I found a magazine article posted somewhere where it was found to retard too soon, in the opinion of the testers, making it more a safety device (I suppose the name says it all) rather than a tuning tool. They suspected it was having problems hearing OK, which convinced me it would have trouble in a B. That said, lots of people with vast turbos bolted to their engines seem to value them.
Steve Postins

This thread was discussed between 20/03/2006 and 25/03/2006

MG MGB Technical index

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