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MG Midget and Sprite Technical - 123 distributor with or without vac?

Yes, I'm thinking of buying a 123 distributor for as it would probably be the LAST part I buy for this restoration... (hopefully)

But which one should I need, with or without vacuum? engine is 1293cc with a 25D distributor with vac, carb is weber 45 on a long manifold and I've got a LCB exhaust.

Alexander Sorby Wigstrom

FWIW I run a 123/tune on my engine. It has a vac advance but not connected, mainly because the maniflow weber manifold doesn't have any provision for taking a vacuum feed.
P Dodd

Always with, no sense throwing fuel away. Can also help flat spots at first acceleration. Especially when it is programmable - you could program it to zero if you wanted. *I suppose, otherwise it is a scam!

FR Millmore

My older type 123 has the vac connected to my Hif44
frogeye Gary

if you need more conformation you could try asking at the 123 forum but note the factory is closed from today until August -

I've got one with vac but had to run it with the vac capped and plugged for a while and it ran fine but having resovle my vac problem by fitting a large bore vac pipe, I think it goes better with it connected but didn't do any checks to confirm this only my feelings and can't really remember

Nigel Atkins

if you need more conformation you could try asking at the 123 forum but note the factory is closed from today until August -

I've got one with vac but had to run it with the vac capped and plugged for a while and it ran fine but having resolved my vac problem, by fitting a large bore vac pipe, I think it goes better with it connected but didn't do any checks to confirm this only my feelings and can't really remember

Nigel Atkins

Thanks guys. A vaccum one it is then. They only differ 50 or something so I might as well go all the way as it will be the last large expense on the car. Except for consumables though. Will also need to buy tyres soon to if I'm ever to get it off the axel stands again!
Alexander Sorby Wigstrom

how worlds (and luck differ) the 123 wasn't a large expense on my car and certainly won't be the last
Nigel Atkins

Leave the vac off Nigel or you may gain another 40 bhp and 60 more mpg, and no one would believe us!

Joking aside we sell 123s with the vac, they dont cost much more and it is always there if you need it for part throttle economy, good with a preset 123 methinks but not so necessary on the programmeable 123 when we can dial as much advance as we can get away with at low cruising rpms.

Peter Burgess Tuning

How can you dial in max advance at x rpm, when that could be foot flat on the floor or hanging out the window?

Faintly related, I am first time venturing into the realm of Puff the Majic Huffer. So, do you have any good references on blower motor tuning, including cam/valve timing fiddles?

FR Millmore


We set the 123 for foot flat conditions. It transpires we can usually pull good advance at lower rpms without detonation problems, this means we do not need the extra advance from vac at part throttles.

For years we have known a B distributor, when the springs are well worn could be say 18 degrees at idle giving say 30 max. If the engine doesnt detonate/pink/ping at low rpms it is very sharp and responsive. We tended to run these Bs without Vac to prevent part throttle pinging/pinking. We can replicate this with the 123 and creep up the advance at lower rpms.

You are right in that we only end up with a flat advance curve not a 3d one. You would need something like mega jolt for that and a lot of patience.

The123 does boost retard with the tune version should a person think they need this facility. We do not find sc engines run enough boost to need this.

No real advice on SCs except ....go for high boost setup around 10+psi. The low boost setups have been disappointing to us for the amount spent.

Peter Burgess Tuning

Hi Peter,
I've put a couple of twists in the vac pipe to restrict the power for road use and save the halfshafts

I've also photoshopped the graphs downwards to make them more believable

I've got a custom non-leaking centre exhaust now so another handfull of bhp added

I've not been able to do a economy test run as it's too much fun keeping the tacho needle moving

until the clutch let go I was putting up a respectable show on a PH run with Porsche, BMW, Caterham, TVR - that's when I discovered for myself that 0w-40 Mobil 1 was too thin, got some NOS Mobil 1 15w-50 in now

Back on subject
I think having a completely new electronic dissy instead of an old dissy or or old dissy with electronic head makes the engine run (much) better and I'm very pleased with my 123

and very pleased with Peter's excellent RR set up (and value)
Nigel Atkins

Thanks for that Nigel, cheque in post :)

I still have to try those leads on an MGB, I am waiting for a suitable dyno session.

Peter Burgess Tuning

at least you got them in the end, try them on something else first

I'm very happy with mine but I think they only added another 3 or 4 bhp to my car, I was hoping for 5bhp as one per lead, but as a mutli-national supermarket tell us every little helps :)
Nigel Atkins

Nigel that may be so, but considering how cheap most of the parts for our cars are and that you can get another brand electronic distributor much cheaper I consider paying almost 300 for a distributor to be a large expense, but that doesn't mean that you won't get what you pay for.

a Swedish supplier of 123 distributors show a variety of different ones for the a-series engine on their website but minispares for example show only two "pre a-plus"

Are there different ones and in that case which one should I use for my engine?

And I assume you can change the program and timing curve with the 123 dizzy in suit and that you don't have to remove it?

Alexander Sorby Wigstrom

Alex, on my early one, you have to take it out to change the curve. But I believe that the later ones are programmable with a lap top in situ. Peter will no doubt confirm. Bit of a shame that if I'd waited another year, I could have had the updated 123
frogeye Gary

There is nothing old with your type of 123!

123 sell different versions
One with 16 fixed curves that you have to remove to change the curve (sh*tty system to remove)
Some of these are tailored for a type of engine but I've always had some trouble getting a real good one to match.
One which is fully programable with a USB connection in the side so it can be done insitu

Both are available in vac advance and non vac advance versions.
Always buy the vac advance version because this gives you the posibility to use it and iirc there is no big price difference
Onno K

Yes Onno, what I meant was that when I bought mine, the USB version wasn't available, which is a shame.
Regarding the vac advance. I found that my red vac hose which came with the 123 became brittle and snapped after a year. I now have a generic vac hose fitted to the unit.
frogeye Gary

I just meant you were luckier than me, 300 is a lot of money (probably more so to me than you even)

basically for you, as said there are two types:
pre-set type which you do have to remove the whole dissy the turn the setting screw but that's only IF required

the other type is the 123 Tune programable which you connect to a computer to tune - whether you need to pay the extra for this type I'd seek advice on

I'd suggest you contact Peter Burgess and see if he posts to Sweden as given full details of your car he'd be able to recommend which type is best for your car and preset the pre-set type - if it costs you extra time and money I think that would easily be offset by the expertise and customer service you'd get from Peter but you can't expect all the advice and back up from Peter if you buy the 123 from elsewhere -

thanks to Peter's rolling road set up mine is fine on the first standard setting

Nigel Atkins

well a few days ago I spotted the CSI ignition supplied either by minpsares or swiftune.. anyone have any experience with that? seems like a nice mod, doesn't have to be removed to change the curve either.
Alexander Sorby Wigstrom

Good searching!
Looks like an other Dutch company jumped in the hole left by 123.
Though I like the product I do not like the 123 company. They are not reachable and do not respond to normal questions.
And they have not touched the big design flaw in there from the start.

I am curious for their custom version and the imobiliser function
Onno K

I also like the idea of the imobiliser, a bit worried though that I'd misplace both code thingys (and my keys).

Haven't heard anything about it until I saw it mentioned on a Swedish mini forum as there's a company over here that sell them too and they also claim to have a custom version but I susspect that they may get them from Swiftune although they offer to map the distributor to costumer engine specs.

Alexander Sorby Wigstrom

As I read it the custom version is a programable versione like the 123 tune
Onno K

You may be right, I've only read on mini spares, swiftunes and westgear (Swedish). Swiftunes and westgear site sais they have there own curves already programmed and so is slightly more expensive than mini spares.

Anyway sounds like a good product, will probably try it out after I've given westgear a call so someone who gets stuff like this more than me can explain it more properly :)
Alexander Sorby Wigstrom

just for info, you probably wouldn't need to go further than the first setting on the 123 so the remoteness of setting on the unit wouldn't matter

good luck with whatever you chances are very high that it will be a lot better than an old, worn and probably never oiled and lubed dissy
Nigel Atkins

Nigel--can you elaborate on "mine is fine on the first standard setting"? If there are 16 settings on the 123, does that mean you used the very first one? The first one is "0" with 38 degrees at 2200.

JM Morris

Peter Burgess who sells the 123 is an expert certainly not me but I can tell you what on the installation sheet

the 16 settings are divided into groups of four, so you'd start at the lowest setting in that group of four relevant to your model

as my model (UK 1275, 1969-1974) falls in the first group it is set at '0' shown as:
'Advance @ 2000 rpm' (crankshaft) - '14.5'
'maximum @ 5000 rpm' (crankshaft) - '28'

I initially installed mine with a mate who know about cars and engines set at lowest group setting for my model and the car went very well one the test run, when I suggested trying the next setting my mate laughed despite my car being above when new figures - mine despite all his experience he was the one who put two HT leads in the wrong order when trying to speed up my very slow and steady pace when working on a car - tortoise and hare :)

I've had my car set by Peter and it remaind on lowest group setting and performing well enough to get compliments on runs with the likes of a Noble, Porches and fast Audis, BMWs, Subarus ect.

mind my car is regulary fully service, maintained and repaired and is driven regularly
Nigel Atkins

Nigel--you and I must have a different set of instructions. The set I inspected on the 123 website didn't have settings for 2000 and 5000 rpm. Yours must be straight from Peter's setup specs. However, if yours is on the "0" setting, my specs are accurate too (according to the website).

I'm surprised these specs are best for you. Correct me if I'm wrong but don't you have numerous modifications off of stock parameters? According to Vizard, when the usual performance modifications are performed, total advance starts having to come down, in the neighborhood of 28-30 degrees total advance. Unless, of course, I'm misinterpreting some how.
JM Morris

Hi Jack,
the figures I gave you where off the leaflet I got with the 123 when I bought it from MGOC, before I knew of Peter

by tomorow hopefully we will have the new computer actually working and I can post a link to the pdf I have as I'm sure it's on the internet but I don't have full capacity to find it until tomorow

my engine isn't much off standard at all, got the 123, K&Ns, Maniflow LCB, performanceleads, NGK plugs, about 30,000 from recon, fully sythetic oil in engine, g/box and r/axle

it's just fully maintained and driven regularly and has the occassional blow out with Nobles, Fezza, Porsche, BMW, ect.

if Peter's about he can give you my figures - not bhp or torque as those mean nothing here or anywhere else - anyawy they're embarasingly high and I've ask Peter not to flaunt them under the noses of others as I'm not one to upset people :)
Nigel Atkins

Nigel those figures where mentione before IIRC and I doubt you have a std cam and or head ;)

But i have seen several different leaflets with 123's and can not find them all on the 123 site....
Onno K

I think I might know where to find the leaflet if I look on was on a retailer's site IIRC

no Onno I was on the rollers again with my improved lubrication and ignition components and the figures increased and losses decreased and that was with blowing exhaust joints

the cam is a poor bit of work I'd sooner have the standard or very near to it and the head work would have only been cutting down on the rough surface a bit

apart from putting miles on I've done nothing directly to the engine other than regular driving and servicing and the occassional blow out
Nigel Atkins

. bear in mind mine unit is 3 years old and things may have changed

. and mine is a side entry cap model

I've found the link to the DOC but it wont let me post it here, so do a search for - mounting instructions for the 123/MID-4-A-V

or try this -

these are the same as the instructions I got with my 3 year old side entry unit

I think I've beaten the computer !! if it wasn't new I'd probably boot it a few times too - gwwwrrrrrrr
Nigel Atkins

woooho ! the link works, now you don't have to disbelieve me or think I've remembered wrong - I have a paper copy in the car's paper files (much more reliable than electronic stuff) and I have paper an electronic copy stuck in two bits of electronic stuff I can't get at unless all goes well tomorrow

new computer with cordless keyboard and mouse and little arieal to plug in the back but they don't work so I've had to plug in the old cordless keyboard and mouse that has a cord to the transmitter !

and they say BL cars were bad when new in the 70s, look at the rubbish we put up with from computers
Nigel Atkins

This thread was discussed between 16/07/2012 and 25/07/2012

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