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 - accuspark electronic distributors

Has anybody had experience of the accuspark electronic distributor , or the conversion kit ?
k proud

I've not but I know a B owner who bought their dissy package (dissy, coil, HT leads, rotor, plugs) he said the HT leads were poor and I've heard the plugs aren't long lasting - but what can you expect at the price

I've not heard back if he fitted the dissy

on my MGs over the years I've used Lucas, Luminition (Optronic, get a spare chopper blade) and Aldon igniter heads and all have been fine

I now have a 123 fully electronic dissy and it's very good indeed (I think Peter Burgess still has a few left) -

(not cheap but do you want cheap)

for HT leads that are well made and look like they'll last decades and they actually do improve performance (British made too) - 'performanceleads' -

should you need a good quality rotor arm or other dissy parts then there's the Distributor Doctor -

Nigel Atkins

Bought Accuspark complete 25d dizzy, works fine. I had no problems fitting it. The quality looks good to me.

RA Potter

I've had three Accusparks. Totally useless. First one didn't work at all and was replaced. Second one worked for a few months and then embarrassingly failed on the MOT ramp. Third one ran
OK for about 18 months and then developed a miss over about 2500 rpm. Replaced with points and no further problems. Don't touch with a barge pole.
Iain MacKintosh

Bought an Accuspark for a V8, didn't fit and had to send it back. I have a very low mileage 123 with side entry cap, if anyone is interested.
Allan Reeling

Thanks guys , as i have been told, mixed reveiws. I know the 123 is highly reccomended but seems overly sophisticated for a 40 yr old car. Im not terribly interested in improving efficiency or performance as i think the claims are over stated. Im just interested in the maintenance free ignition aspect as compared with traditional contact breaker .
k proud

What makes you think the claims are overstated?
The life expectancy and quality of the Accuspark are suspect as is the timing curve.

Peter Burgess Tuning

I've got a 123 and I don't think I ever overstate the claims I make for it as I only say that it improves the running of the car noticeably

if you've got a standard B engine even in good condition adding bits to it are only going to make very small improvement to performance and efficiency but the more you do the more the accumulated effect but depending on what these are it could still be very small

full and proper servicing, maintenance and repairs along with regular reasonable distance use all year around are the best things as tuning agents and form the necessary base to proceed to the incremental improvements mentioned

I swapped from an Aldon igniter head which was fine but it was fitted to my existing old mechanical dissy body which IIRC were well out when new after only 3 + years

I can't tell you if the 123 has improved MPG but I guess it would if I didn't keep taking advantage of the improved performance in other areas (from starting, tick over to all through the rev range)

I think it would even help in a ropey engine in a ropey car but Peter would know that much better than I

>>on my MGs over the years I've used Lucas, Luminition (Optronic, get a spare chopper blade) and Aldon igniter heads and all have been fine

I now have a 123 fully electronic dissy and it's very good indeed<<

Nigel Atkins

>>Im just interested in the maintenance free ignition aspect as compared with traditional contact breaker.<<

I've just thought, if you also mean inexpensive then the obvious answer is Powerspark (for an igniter head at least)

these often get recommended by posters on here that use them (although I've never used them)

as with all these units it is important to install them taking care to allow for plate movement and prevent scuffing of the delicate wires inside or outside the dissy

in my personal opinion those users of good quality igniter heads that have problems often blame the unit rather than poor installation
Nigel Atkins

If you opt for an Ignitor type system, you might care to look at the Aldon Amethyst system, this uses the original dizzy with your (new) ignitor and allows you to set the curve for your engine-if you are so inclined.
Michael Beswick

OP has put (referring to the 123)
>> I know the 123 is highly reccomended but seems overly sophisticated for a 40 yr old car. Im not terribly interested in improving efficiency or performance as i think the claims are over stated. Im just interested in the maintenance free ignition aspect as compared with traditional contact breaker.<<
so I don't think he would be inclined (based on above)
Nigel Atkins

The Accusparks units I used were in my roadster. Perhaps I should have mentioned that I have a Lumenition Magnetronic unit in my GT and it has performed faultlessly for the last 12 years. I would therefore have no hesitation in giving it my full recommendation
Iain MacKintosh

"What makes you think the claims are overstated?"

I recall you saying the curves are not as described in the documentation.
Paul Hunt

I think we are talking about performance. The 123 outperforms points and basic electronic distributors. The problem is with any distributor folk expect to set them at idle (whatever that is) and then assume all the rest is ok. I do not think the data from BL is any better, there is usually a +/- 2 degrees which gives a 4 degree difference does it not. Therefore the curves cannot be the same as BL ones as the BL ones are not specific when you actually look at the data the Pirates Code....more a sort of guide. As the 123s are more specific they cannot be the same as BL curves as they do not seem to have an inbuilt fudge factor to take into account inconsistancies of springs and bob weights.

Peter Burgess Tuning

Thanks again guys, feel like ive opened a can of worms & im still confused.I must admit im leaning towards the magnetronic that Iain mentioned . Three times the price of the accuspark, powerspark etc so i suppose in theory should be better although basiically the same system.Also read about the petronix , anyone know anything about that baby ?
k proud

Hi Ken, I have had a Powerspark electronic ignition conversion on my 1976 MGB for 3 years now with no problems at all. It is simple to fit and very reliable

If you want something simple that utilises the old distributor and does away with the points, then this is ideal and good value for money. I purchased another kit as a spare, just in case I had a problem and have never used it. Suggest you renew the distributor cap and HT leads whilst you are at it.

Andy Robinson

I don't know anything about pertronix but I see the Distributor Doctor sells some of them so assume they're not rubbish

I'm not sure their special coils are necessary for road use

again for HT leads - for HT leads that are well made and look like they'll last decades and they actually do improve performance (British made too) - 'performanceleads' -
Nigel Atkins

Petronix Ignitor is a US bit of kit. Here Aldon do the same thing. I bought mine several years ago when the $/ was good. The unit was actually shipped from Hampshire.

They use a collar that slips over the dizzy shaft beneath the rotor arm that activates the trigger mounted on the base plate, as do many of the ones discussed above. Are they better? who knows- but you tend to get what you pay for, and whenever something becomes successful, other cheaper copies turn up,many of which are made to the cheaper price. A case in point is red rotors. They used to be a sign of a good one, now every TDH produces them..

None have to be used with a special coil; they simply are fit and forget with no maintenance. In themselves they will not improve nor spoil existing performance.

The ignitor is very easy to fit, tho there have been instances where fitting this type of electronic ignition has necessitated re-timing and/or messing with the tach.

(My Petronix was fine)
Michael Beswick

Petronix is now on my V8, easy to fit and no issues so far, but the rotor arm does seem to be higher in the cap, therefor harder against the carbon contact. Whether that proves a long term problem, we'll wait and see!
Allan Reeling

taking up what Michael has put the retiming could be because the CB point were previously worn so fitting new whether new CB points or electronic would necessitate retiming

settings are in this order and if you adjust one item in the chain then you'll need to check or adjust all the items that follow in the chain - tappets, CB points, plugs, timing, carb mixture

fitting the igniter head should improve performance in as much as it's more constant and doesn't vary with the wear of the CB points - of course you still have the rest of the variables of wear and settings on the rest of the mechanical dissy

I'd also remind you that whilst installation of the igniter heads is simple on units some don't allow for plate movement and scuffing of those delicate wires and then blame the unit for being faulty and some you can kill by wiring the wrong way
Nigel Atkins

Retiming being found necessary, where the previous timing was correct and you carefully marked the relative positions of distributor body and block, is caused by the new device having a different trigger point relative to the lobe of the cam compared to the previous device - rotor phasing. This causes the spark to occur with the rotor at a different position relative to the cap contact. A slight difference doesn't matter as phase change occurs with varying vacuum advance anyway, which is why the rotor has a relatively wide arc and why there is usually burning around most of the arc. Phase change doesn't usually occur with varying centrifugal advance, only vacuum. Some electronic triggers have been found to be so far out that the spark occurs when the rotor is between cap contacts which causes very erratic running. But even if moderately out the trigger point can occur when the rotor is not overlapping the cap contact at one extreme of centrifugal advance or the other, which increases the total gap in the HT circuit, which increases the peak HT voltage. If the voltage gets too high that's when you get breakdown of the rotor, cap, coil or coil lead. Over many cars and rotors I've often noticed this burning goes right to one edge of the rotor, with the other edge being clean, indicating that perhaps the phasing with points has not been ideal.
Paul Hunt

I'm currently using a Lumenition Magnetronic, I've had it fitted for a couple of years and it's performed faultlessly. They're a bit expensive but mine came fitted to a second engine I picked up for spares.

One thing you do need to know about with the Magnetronic unit is that it has a fixed and rather long dwell angle, 70 degrees from memory. This seems to work well in my engine giving good power all the way to red line. I've not had any problems with this but the coil does seem to run a bit warm and it could be an issue in slow moving traffic in hot weather.

I tested an Acuspark Stealth unit as they claim it has variable dwell. They're correct in that it does have variable dwell which is achieved using a fixed closed/charge time of (from memory) 5mS. The unit I tested was a bit over the 5mS at the bottom end and a bit short at the top end. Giving the effect of longer dwell at the bottom and shorter at the top. I can't comment on what effect this would have on power as I was only measuring distributor characteristics.

The Acuspark units are about a third of the price of a Magnetronic unit and although price isn't necessarily an indication of quality or reliability I think it's a case of caveat emptor. I always carry a set of points and a condenser just in case

I'm careful not to suggest that being cheap (price) isn't misconstrued as being cheap quality, the last time I did this Mr Tony Ibbotson had a go at me, although as he later admitted it had more to do with publicity than anything else.

I'd like to run some tests on an Aldon Amethyst if someone wants to donate one, the management (aka SWMBO) wouldn't sign off my expenses for one though.

R.A Davis

so k proud what are you going to buy or have bought?
Nigel Atkins

K Proud, I still have the 123! With vacuum and choice of accurate advance curves!!
Allan Reeling

70 degrees is a very long dwell, almost 40% longer than a 45D4, and 15% longer than a 25D4. It significantly increases the heating effect in a coil, particularly a 12v coil i.e. without external ballast i.e. chrome bumper cars originally.

But measured coil temperature is very much dependent on ambient temperature - the coil on a running engine will always be higher than the air surrounding it, and it's in the engine compartment behind the radiator. Last January in an ambient of less than 10C my roadster (unballasted) and V8 (ballasted) only got up to about 40C which is hardly more than warm. But in July with an ambient of 26 or 27C the roadster got up to 67C and the V8 62C, which is too hot to keep a finger on. But these cars run in desert states with ambients of 40C and higher without problems, so no one should get a problem with coil temperature in the UK - with the factory dwell at any rate.

The factory 45DM4 electronic system used on North American spec cars is a variable dwell system that gives about 5mS coil energising time per HT spark through most of the rev range, reducing slightly at the top end. Points by comparison on a 4-cylinder engine with a 25D4 distributor gives about 30mS at idle, reducing to 3mS at 6000rpm. Lucas state that points ignition is perfectly satisfactory on a 6-cylinder engine up to 8000rpm, by which time the energising pulse has reduced to less than 2mS. This is similar to the V8 at 5600 rpm, and that has no trouble at all revving past the red line if you aren't paying attention.
Paul Hunt

I'm aware that 70 degrees is significantly longer than standard which is why I mentioned it, I've checked my notes and mine averages 72.5 degrees across the rev range.

"measured coil temperature is very much dependent on ambient temperature" this is simple physics. The rate of dissipation is proportional to the difference in temperature of the objects, therefore in cold air conditions the coil can dissipate the heat more readily that when it's hot. That's why I wrote "it could be an issue in slow moving traffic in hot weather" . In fact Lumenition themselves acknowledge this could be a problem by stating their Optronic variable dwell systems "prevent the coil over heating at low engine speeds"

What dwell/system are you running in your cars?

The main issue with electronic ignition systems is when they fail it's generally sudden and terminal, unlike points that(generally)fail gradually with a lack performance. However the upside is no maintenance once fitted, full performance for the life of the device and consistent timing. I'm happy to take advantage of these benefits but I always carry(as yet unused)a set of points and a condenser, which I think I could fit in about 15 minutes.

There are people that wouldn't think of fitting anything other than points, likening electronics to the work of the devil. If it's for originality, I'm ok with that but the only reason points were fitted originally was there wasn't a better system, things move on. If this wasn't the case we'd still be using low tension ignition, trembler coils, hot tube or even flame ignition. And while I'm on my soap box, what about cross ply tyres, white metal bearings, splash lubrication, rod/cable brakes, I could go on. Even my lawnmower uses electronic ignition.
R.A Davis

Hi Nigel , no decision at present, have been fasinated by the wealth of varied info that has poured in. Im not in a hurry as i have more urgent non mg matters to attend to at the moment. I have noted however that mgoc are offering 15 off the usual price of the magnetronic at the moment.
k proud

"Optronic variable dwell systems "prevent the coil over heating at low engine speeds""

That's quite possibly true in the case of the 70+ degrees dwell with their fixed dwell system, but no one should have coil problems with an ignition system that uses the factory dwell, especially in the UK.

American-spec cars got electronic ignition as they were required to travel 50k miles without any adjustments. The recommended points change interval is 12k but I've run mine as an experiment for far longer than that before I noticed any change in running, and that was only the roadster taking a little longer to start. The roadster set stayed in spec for dwell for the whole of their life, and although the V8 set did need one tweak because of their narrower band they are simplicity itself to alter given the hex adjuster shaft on the outside of the distributor. I've never (so far!) had points or condenser fail in use in well over 40 years, and I regularly get mid-30s mpg out of the roadster and have had 40+, and 30+ from the V8.

Many claim how much better their car performed with a new ignition system, but then most are comparing with a knackered or poorly set-up old one so it's hardly surprising. Most electronic systems will not improve ignition over correctly set points, as most electronic systems are simply a transistor switch that has exactly the same effect on the coil as points. Well, I say exactly the same, but to be strictly accurate a transistor switch results in lower current through the coil and hence a lower energy spark as the transistor has typically ten times more 'contact resistance' than said decent set of points. That's one of the reasons why the factory eventually fitted low-resistance coils to American spec cars, to counteract it.

While I can still get reliable points, I'll continue to use them, but that's just me.
Paul Hunt

There are several factors which affect the timing and reliability of the ignition system.

1. The mechanical drive via timing sprockets, chain and skew gear - these remain whatever distributor you fit.

2. The centrifugal weights, springs and shaft bearings - these can be stiff through lack of lubrication and springs can be stretched or broken.

3. The vacuum advance capsule and the baseplate - these can be inoperative or stuck

Replacing points with the Aldon / Lumenition / Petronix etc electronic units only replace the points - all other factors remain.

4. The points / condensor / rotor arm - failing condensor, drag and points bounce as well as erosion will affect performance.

Fitting a totally electronic unit like the 123 will eliminate 3 & 4 but not 1 or 2.

Fitting a EDIS system eliminates all issues - the trigger is taken directly from the crank and the advance can be mapped to as many rpm points as you like, each plug has its own coil so charge times aren't an issue. Additionally the ignition map can be adjusted by load - either via a manifold pressure sensor or a throttle position sensor.

The 123 is expensive for what it is - if you want to spend that much go for the EDIS - otherwise use points or the Aldon/Petronix and maintain the car as it was designed to be.

Chris at Octarine Services

cheers Ken

Chris, not 2?
Nigel Atkins

Oops well spotted - yes obviously 2 will go!
Chris at Octarine Services

I wish I could spot my own typos :-)

2 is also an advantage a fully electronic dissy has over just fitting an electronic igniter head
Nigel Atkins

How long does it take to fit a complete eddis system from start to finish in comparison with the time taken to fit a 123? Same for acquisition, how easy is it to collate the parts for the Eddis?

Peter Burgess Tuning

Fitting an EDIS system takes much longer than dropping in a 123, depending on how you trigger the crank - a trigger wheel needs to be fitted to the front pulley or the flywheel and the sensor mounted - but I fitted one to a supercharged B in less than a day and that included setting up the initial map.

The parts are fairly easily acquired - Matt Kimmins was doing a kit (don't know if he still does them).

Chris at Octarine Services

a day (for an expert) is a very long time compared to fitting a 123 and even fully setting the 123 up

what you must remember Chris is that you know exactly what parts you require and which parts work together and where to source them, if the car owner doesn't have this info and fitting skills then the eddis system seems very complicated and with expensive labour costs to install

whereas even a total non-mechanic like me could install a 123 and have the car running and even allowing for a proper rolling road set with Peter I'd be at a country pub for a quick lunchtime half with the car fully set up and tuned with minimal labour costs

or if possible buy the 123 from Peter and have him fit it and tune up on the rolling road for same costs and time, still be in the country pub for lunch without even getting your hands messy
Nigel Atkins

Another recommendation for the magnetronic from me. Installed mine in about 1998 & never had any issues with it. Its not effected the life of my coil despite the annual pilgrimage to LeMans in temps of 35 deg c some years & slow moving traffic. Would recommend it as the first upgrade to any MGB owner.
G Britnell

I have just fitted a Aldon Amethyst to an 18v motor in a 74 . To fit it you use your old dizzy and lock up the advance weight at full advance and disconnect the vac advance. Also remove the capacitor. I have a new Lucas dizzy that has only done 3000 miles and broken down twice putting me on a flat bed tow truck once. Just love the quality of new parts. This was a good candidate to rip the guts out of. The Aldon unit will work with most electronic triggers replacing the points. I looked at the 123 but decided to go this way . The unit is mounted inside the cab so I can connect a lap top while driving. It is programmable in 14 steps from 500 to 7000 RPM and vac advance is also programmable. Has rev limiter and variable dwell. It will store up to 8 programs in it. Operating instructions are a bit optimistic just select file and it will open. Like hell. It is a Jave file and you need to load Jave on to your computer, but this is free. Also you can load files with advance curves from the unit to computer and computer to unit. I have found this a bit useless as the unit does not want to recognise the files in the computer including the ones down loaded from the unit. Even with these small problems I am very happy with the unit as the car is finally running well after how many dizzys all with problems. There is no rolling roads here that I can take the MG to so this unit lets me fiddle about with the setting on the road. Also a PO built to motor so I have no idea of specs to have a dizzy built for it. It is still pulling and not revved out at 6500 RPM.

With an electronic points trigger it overcomes from Chris list
Point 1 None of
Point 2 All except for shaft bearings
Point 3 All of
Point 4 All except for rotor arm
Longevity of the unit? Who knows as it is new on the market.
K Stuckey

Nigel - it all depends what you want from the set up - I am just saying that for the most accurate ignition timing then the EDIS is best - if you want simple then stick with points and change them as per the maintenance schedule - if you want simple low maintenance then go with the Ignitor / Petronix.

I see no advantage to the Optronic over the hall effect units. I have also seen two optical units fail.

The 123 is expensive and their track record with me is poor - 1 dead out of box and 2 that malfunctioned - I won't fit them.

Accuspark - I have fitted one and it is still running just fine.
Chris at Octarine Services

"disconnect the vac"

Move the vac pipe from the distributor to the Amethyst unit.
Paul Hunt

fair enough Chris

my experience and knowledge of 123 is that they are good but not cheap whereas my acquired knowledge of Accuspark is the reverse but perhaps I've only heard about the ones that don't work rather than the ones that do

OP wants something cheap to buy, unfortunately that doesn't always work out overall
Nigel Atkins

This thread was discussed between 05/12/2013 and 20/12/2013

MG MGB Technical index

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