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MG Midget and Sprite Technical - Distributor - which one
Many thanks for your help with past questions , think im sorted on wiring loom now.
Am planning 1380 fast road engine with 45 dcoe weber as salvaged from donor car but am unsure about distributor - which one should i use .
I think im right in thinking with weber no need for vacuum advance but unsure past that point
Andy help greatly appreciated
|A 123 is programmable with 16 curves, you can even get one where you can make your own setup with a pc. The compression plays an important role in programming the distributor.|
|Flip Brühl 948 frog 59|
I was going to ask the same question. My engine is not quite as hot as yours but my dizzy is well worn. Does one go for a rebuilt dizzy from the dizzy doctor or Aldon? Or a new one from MGOC, Moss? Or a 123 or 123/tune?
Too many options.
By the way I think you are right that you don't have vacuum advance with a weber.
|Go for the 123 tune!|
I am banging hy head against the wall now having bought 2 123 ignitions last year and now they have come with a programable one!
Trying to get in contact with them to see if they will exchange but they are hard to reach.
|Of course you need vacuum advance with any kind of carburettor regardless.|
The vacuum advance is designed PURELY to give better fuel economy why would you not want fuel economy simply because you fit a weber?
Maybe that is where the urban myth arrises from that webers are heavy on fuel.
Regarding a dissy. If you are serious about max power then as stated above CR is extremely important.
Programable ignition is the bestt you can have, if you can not afford it then just a quality dissy will surfice IMO
|Bob Turbo Midget England|
|I'm with Bob. Unless you can fit the 123 with a vac unit, I'd find a spec from Aldon that matches your engine, and use an ignitor.|
|Bob, my Sprite has a 45DCOE and the distributor has no vacuum advance - one day maybe you'll get to go for a drive with me, or someone like me, and afterwars you'll agree that in some instances vacuum advance is pretty much going to be redundant!|
|I suppose Daniel if you are either flat out or off the throttle then I would have to agree vacuum advance is a waste of time, although even then it could smooth out the idle. :)|
|Bob Turbo Midget England|
|Go for the 123! My 1430 has a 123 (with vac unit) and it brings me so much joy every time I start her!|
The purists will say that a good setup with points is as good as an electronic device, but I'm happy to be rid of the hassle!
|Dizzy curve depends on factors such as cam spec, CR and head - sort those out before you worry about dizzy spec (or get hold of a 123 and you can adjust to suit) :)|
We're not allowed programmable ignition in the midget Challenge but if the engine's flat out between 5000-8000rpm all the time it doesn't really matter that much...
|I'm not certain but think the best average fuel consumption I get is about 27mpg this is with a 5 speed on a 3.9 diff. Nuff said?|
|Let's tally up where the votes are so far:|
for a modified engine, you need to modify your advance curve, which can be done with a standard, mechanical distributor, but is difficult to do (really ought to have a rolling road, and a distributor curve machine, to get the springs and weight changes right).
Or, you can use a programmable distributor like the 123, and then all you need is a rolling road session and try the different curves until you find the best fit.
While there are lots of places you can get mechanical distributors from, Mallory, Lucas, Aldon, etc. And these can be had with solid state points, you still have the problem of modifying them to give you the best advance curve for your particular engine.
There are "outboard" ignition systems that you can add that will allow you to adjust your curve, but they require an additional box be added in the engine room to house the electronics to handle that.
As far as I know, only the 123 gives you the ability to re-curve the distributor without having to trial and error with lots of springs and weights, and allows you to do that without having to add an additional box under the hood.
So, my vote, for a heavily modified engine, which yours sounds like (new cam, head work, etc.), is a 123.
This thread was discussed between 02/09/2010 and 03/09/2010
This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.