Electronic Ignition

Thanks Chris.

Here is an extract from mg-cars.net posted by Peter Burgess (I assume it did come from the MG guru)

"You need to restrict the pipe till the vac gauge is fairly steady otherwise the flickering will be too much to give any meaningful info.

What timing light are you using to tell you 14 degrees or 30?

The most important thing is dynamic timing, what does the advance go to at say 2000, 3000 and 4000 rpm? If the advance curve is malfunctioning maybe you have 14 everywhere whereas 30 everywhere may have been better. Check with no vac.

You have to state accurate measurements to get help online as all is guesswork unless we are playing on a level playing field. Even then it is impossible to tell you what curve you need. Timing variation of a couple of degrees can make or break the performance of an engine. Your max advance requirement will fall, roughly, into a band of 25-40 degrees depending on your specific engine needs. Anyone that tells you exactly what it should be is talking rubbish."

The general consensus seem to be that ignition timing is more critical than fuel mixture (within reason) for both fuel economy and performance and this is supported by dyno comparisons.

I think as you know your distributor springs are good, the car starts and runs well at 10degrees BTDC static it's probably best left alone (apart from fitting your new bits from Distributor Doctor)!

David

I recall Peter Burgess was supplying 123 ignition systems, not sure if he still does but his prices were the best I found in the UK. I assume you will probably want to go for the "Tune" version so you can set your own curves. Burgess

Another cheaper option that allows easy set up is the Aldon Amethyst. It gives you full control over the advance curves and has versions for vacuum or TPS load sensing. It can be triggered by most distributor - points, hall, optical, reluctor etc. Amethyst. It retains your original distributor and you simply lock the mechanical advance weights.

David

Hi,
Contacted Peter Burgess he doesn't sell 123 dizzy's any more, got onto Australian 123 Dizzy stockist and it's in the post as I write, reading everyone's experiences has been really helpfull in deciding which product to choose.
Should have 123 fitted to ute soon will post when it's a goer.
Next question, there's 16 ignition settings on 123 which one do you 123 users recommend.
Regards Simmo
(5-0)

Simmo

I recall that you have twin SUs and a S type exhaust manifold which means the advance curve should look like the MGB, needing a little more advance if you still have the Landcrab camshaft. Unfortunately you will need to experiment as there is no one perfect curve, each engine differs. You may have seen this quote from Peter Burgess before "timing variation of a couple of degrees can make or break the performance of an engine. Your max advance requirement will fall, roughly, into a band of 25-40 degrees depending on your specific engine needs. Anyone that tells you exactly what it should be is talking rubbish." This is why I suggested the 123 Tune version where you program your own curve, usually by tweaking a preset value.

However what is important is that you do not exceed the maximum ignition advance as this is where damage would occur under high rpm and load.

The MGB forums indicate that when setting the initial idle timing at 10 degrees BTDC that the curves C,D,E,F are likely to be most appropriate. If you have the S type camshaft, probably D or E and if the original landcrab cam then F gives more low down advance and may be better suited. You can also advance the idle setting to 12/13 degrees at most to tweak it a little. If you hear low rpm knock then go back progressively to curve C. If you should get knock at 3000 rpm or above (assuming you can hear it)then either retard the initial idle setting or if this causes poor idling switch to curves group 8,9,A,B and keep the idle at 10-13 degrees.

It would be interesting to hear about your results.

regards

David

I've just found this link on ignition timing that some of you may find interesting. Although it relates to a modified MGB engine the comments from two well respected experts show the importance of getting the ignition timing precisely right (although admittedly more critical on a tuned engine) but also a possibly overlooked cause of ignition scatter, the drive gear for the distributor. So those experiencing problems after rebuilding distributors, take note.

Ignition Timing

David