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MG MGB Technical - Which Electronic Ignition

Hi all

MGB 69 standard gold seal replacement engine.

I intend to use the car on a regular basis for normal road use.

Which make should I go for given the use as explained above.

I have had a Powespark ignition the the midget, that has been reliable but it doesn
Tony Brough

if you just buy the igniter head it leaves the rest of the dissy old and worn. The dissys were know to be out of wack within a few years of the car leaving the factory. Then if you add lack of owner/user maintenance on they could be bobbling along more than you realise.

For fit and forget, liability, better start up, tick over and response throughout the range, no servicing (other than cleaning dissy cap and rotor perhaps) - get a fully electronic dissy, doesn't need to be programable for road use.

There's CSI and 123.

I have a 123 in my Midget, before that I had an Adlon igniter head system which was good and many years ago a Lucus strobe system igniter head system that was good but neither were as good as the fully electronic 123 dissy.

I can't remember what I put in my B as it's too long ago and my r/b roadster was already electronic again too long ago for me to remember ... now what was I going upstairs for(?).

(both nl)
Nigel Atkins

ETA: Have your tappets adjustment checked before fitting the fully electronic dissy and once you've got the dissy set right you can forget it from there on.

Also your B will run better just from regular use - and so would your Midget.

Nigel Atkins

I fitted Accuspark to my 45D dizzy and I have a spare Accuspark(only 35£) in the car. If the one in the dizzy would fail I only have to unscrew 2 screws, fit the spare module and I am on the road again.
Some other electronic ignitions costs you an arm so you dont buy a second spare ignition. If it fails on the way...
H. Jorens

Nigel Atkins

I'm a bit of a Powerspark fan
Fitted quite a few and haven't had an issue
The wiring is fairly light on so a nice free loop in the dizzy so it doesn't get worked too hard with the vac advance and support the external wiring so it doesn't wiggle itself to death
As Nigel noted the rest of the dist. needs to be up to scratch for best results though
Powerspark also sell a complete brand new electronic distributor for MGB for around 70
(haven't got a pounds thingy on my keyboard)
William Revit

Never had points or condenser fail on me in over 50 years, and using dwell to check the gap I find I don't need to adjust them at annual services, and when they do eventually drift out they are beyond the normal replacement interval anyway.

If you get a problem with them on the road it's usually easy enough to get you going again, once electronics fail - and they do - it's usually terminal and you are stuffed unless you carry a replacement.

I must admit I'd totally forgot about Accuspark dissys. I was always concerned, possibly unnecessarily but I don't know, about their retail price and the price of the complete packages of ignition parts.

I know of a couple of IIRC B owners reporting the HT leads not being the best quality straight out of the box and I wonder about the quality of the plugs too - but don't know.

If they're fitted to classics that are usually static and/or never driven in a spirited fashion might they be fine, not enough reports back that I can remember seeing.

For a car that I was to rely on for real daily use, as I used to with my classics in the past, I wouldn't feel I could trust them, but I could be wrong.
Nigel Atkins

Paul, for adjustment and failure are you including (fairly) recently made points and condensers or stock you've had for a good number of years?

As you know but others might not, we totally differ in our approaches, I do not carry any parts (other than bulbs that I've never used on my car) and never look forward to any roadside heroic repairs where I'd be able to use them, I've had enough roadside repairs on classics to last me two lifetimes.

Yes when the electronics fail if you don't carry spares of it you're stuffed - but - whilst I can't match your 50 years I can go back IIRC 30+ years of electronic ignition without any roadside failure (or any failures but not the same vehicles over that whole time). The trick is to replace before this happens, or just accept recovery if it happens, prevention is better than cure though.

Two different views, and we'll never agree but we're both right and wrong in our own ways and can as usual agree to differ without rancour. :)
Nigel Atkins

After many episodes with points collapsing with my new distributor I switched to a Luminition set up. That was 16 years ago. Haven't had a problem since.


79 MGB
gary hansen

I understand what Pauls says about points and condensers theyíre simple and relatively easy to replace but unless youíve got a stash of new old stock parts, reports suggest theyíre just as much a lottery as cheap electronic units.

Iíve tried a number a different electronic modules with varying results, including Accuspark standard and Stealth, Lumenition Magnetronic, Powerspark and my own design. Iíve had varying results and my tests lead me to the conclusion that I wouldnít use the cheap units. Iíve had a couple of failures, fortunately not complete dead on the road type but misfires when hot, dwell angles either not what theyíre claimed or too high.

Which ever route you take I think itís important to ensure the mechanical parts are up to scratch. Electronic units can possibly take care of timing scatter but they canít help with advance, either auto or vacuum. Having a good spark is important but having it at the right time is just as important. I understand that modern fuels might require slightly different advance curves but my experience leads me to believe the standard curve for the engine will give fairly good results.

As most people set their timing at low engine speeds, worn out (stretched) advance springs will result in max auto advance being reached to soon and to little. Thisíll make the engine fell sluggish and lack top end power.

Little or no vacuum advance wonít affect power but it will affect cruising economy, too much vac advance will cause the engine to pink, lose power and possibly cause damage if allowed to continue.

For these reasons I canít understand how the cheap suppliers of complete distributors can suggest that one distributor is suitable for almost any car.

This is why Iíve now fitted a CSI unit, I chose this because they supply you with all the advance curve info, it looks like a 25D even down to the (fake) vacuum module and it works.

I find it strange that people will spend money on exhaust, cams, carbs etc in pursuit of a bit more power and forget that unless the spark is at the correct time, your wasting your time.
R.A Davis

I know new stuff particularly ignition components from other than Dist Doc can fail in a few miles. The last time I changed the points on the roadster was in 2008 which is now 21k ago, not needed to adjust since then. It said 'Turkey' on the box, I did wonder whether that was a comment on their quality but apparently not. I did get a new condenser before that in a fit of madness when I treated it to a new cap, leads and rotor for no real reason, won't be doing that again. I do carry a spare distributor complete in case needed.

I can't remember changing points on the V8, the only record I have of buying a set was as a spare when I got the car in 1995, but that was 100k ago so I must have done them at some 'point'. Being a V8 they have a narrower tolerance band for gap/dwell but that distributor has an external adjuster so the dwell is easy to reset on a running engine. Condenser has never been changed on that, but I carry a spare as well as points.

To be able to replace something just before it fails really would be a good trick!

Just fitted new 25D4 points/condenser from Powerspark to a pal's TR4 and they were hopeless. The tags had been wrongly positioned so the were under the cap and the condenser wouldn't sit in it's slot. With that sorted the end of the points spring as it came round the insulators had the end sticking out and touching the fixing screw while the gap was still way too big i.e. shorting them out as well as not being able to set the gap. On mine the end comes round further and although it then turns out it is lying flat against the main part of the spring well away from the screw. Even with that bent out of the way I still felt the loop of the spring was too close to the screw with the correct gap, although that may be because his screw head is bigger than mine, when one would assume the thread is the same. There was also a big washer under the spring washer that was fouling the points spring, which we removed.

His starting had always been iffy, only firing as he released the key, which said to me weak spark, then it wouldn't start at all just the occasional cough and spark. In the end we found the front carb was flooding which isn't obvious on his Strombergs without an overflow pipe and with mechanical fuel pump, dirty/high-resistance pints which were cleaned and reset, and two open-circuit plug leads where the silicone core wasn't trapped under the crimp so he got a new cap and leads with rotor for good measure ... and it was just the same. With two colortunes in and a timing light on a 3rd lead I could see that firing was very erratic, hence the new points and condenser although I'd already tried adding a second condenser which didn't make any difference. After getting the points sorted it fired up instantly i.e. while still cranking as it should, and on a test drive he said it was miles better than it had ever been. I reckon the very narrow gap between his old points spring and fixing screw or big washer had been breaking down with the 200v or so that appears across the points as they open to generate a spark.

The electronic under-cap units can shift the trigger point which is why people say they have to adjust the timing by quite a bit afterwards even though it was right before. If this moves too far the spark can occur when the rotor is no longer alongside the cap contact, which risks the spark failing altogether. I had one sent to me where it was so far out it was between cap contacts.

The centrifugal advance system (but not vacuum advance) moves the trigger point as the revs change, which is why the rotor contact is as wide as it is. Ideally there should be evidence of burning in the central section but not at the ends, but in practice it always seems to be biased to one end, i.e. the rotor may just be starting to move away from the cap contact at that rpm.

Do you get 'Fuelmiser' brand products over there--Their ign. points are spot on quality
Really well made and the contacts line up perfectly, they do condensers as well but I don't know what they're like--ok I would guess
William Revit

Thanks for the feedback.

As my dissy is old and worn I have gone for a replacement dissy with electronic innards from Powerspark. I can always keep the old dissy as a back in the care, just in case.

I will give this a try for a while to see how it performs. If Iím still not happy, then maybe I will try 123 or CSI.
Tony Brough

Not heard of them, Willy, and Googling only shows au and nz sites. Which reminds me of another issue with the Powerspark points - the contacts are not in line. Enough of an overlap to work though for a while at least and he is intending to sell it.

One wonders at the quality and the curve of a new distributor plus electronic module for £70, the modules alone are about half that. One hears of China and India knocking basic distributors out for about £5 a piece. Fully electronic are about £250, but at least with the programmable type you can create your own curve that suits your engine and fuel.

I'd have mine rebuilt by Dist Doc as he supplies the correct springs as well, and stay with points while I can get them and they work.

let us know how you get - which I guess really means if you get a problem as otherwise you'd have to keep coming back to say "still working well".
Nigel Atkins

>>To be able to replace something just before it fails really would be a good trick!<<

Now, now, tut, tut. Yes it'd be a reasonable but not necessarily a good trick as the item may be well be passed it's best or optimum and perhaps giving reduced, poor or declining performance well before failure.

I put to replace before not just before, do you not ever replace items as preventative maintenance, do you test your engine oil before replacing, if not I can put you on to a kit to do so, but how often would you need to check to find the point just before failure.

Sometimes it depends on the level of performance, low or high, that you are prepared to accept, sunny Sunday afternoon bimbles to the local car show will be lower than for regular spirited driving, as proven by the running condition and performance of many classics.
Nigel Atkins

R A Davis, excellent post, read it again everyone.
All I would add is that timing scatter most often derives from wear in the drive to the distributor, especially the gear on the camshaft. I have list count of the number if times a new camshaft has eliminated scatter when other measures had failed.

And right on the nail about the cheap one hat fits all units. It's a nonsense. They have 10+ degrees too much advance for a B - a good way to damage your engine.
Paul Walbran

I can't think of anything I replace purely for preventative maintenance except oil and filter, only if there is evidence of an issue. I certainly don't test the oil and I have no interest in doing so with engines as old or as agricultural as ours. For reasons I won't bore you with I ran the V8 plugs for 25k before they started giving hot start issues. The roadster had Bosch 4-point plugs for 40k before I could detect a slight misfire at manoeuvring speeds. The standard ones that are in both cars now could well see me out! Roadster points I change when they have gone out of tolerance - assuming they have also gone beyond 10k by that time as there is no 'point' in going through the faff of readjusting them. V8 points ... as I say I have no idea when I last replaced them as they are easy to adjust. Both my cars go really well and give good mileage, but that's subjective, if Peter Burgess was nearer I'd probably put them on his rolling road out of interest.

I had timing scatter on the V8 until I replaced the cam gears and chain for other reasons, then it was rock-solid - for a few years and thousands of miles then it starts coming back. Unless you are trying to get the last ounce of performance out it's not really an issue, and that doesn't interest me.

This thread was discussed between 10/09/2019 and 12/09/2019

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