MG Car Repair: Ignition timing and CO setting for MGB with Stromberg, vacuum pipe, maximum advance

Question
QUESTION: We have a 1976 MGB with rough idle static timing is 10 but after you start it it goes beyond the timing marks something like 50 or more advanced and is not smooth. This is not points and has the single carb as we have no control over CO I think this is dist related any help would be appreciated

ANSWER: Hi P.  I presume you are using a stroboscope.  In order to check timing with the engine running, you must temporarily disconnect the vacuum pipe from the distributor.  The timing should then be steady, increasing as you raise the engine speed.  Check it out, and get back to me if it is still unsteady with the pipe disconnected.

The timing should be set to 10 degrees at 1500 rpm, and the distributor is OK if it rises to about 17 degrees at 2,000 rpm.  Maximum advance should not exceed 37 degrees at 4,500 rpm.

Remember to re-connect the vacuum pipe when you have finished.

By the way, you do have some control over the CO if you adjust the mixture.  To do this you must disconnect the air pump and plug the injector pipe.  You should be able to get it down to between 4.5% and 6.5%.

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QUESTION: There is no vacuum to the dist it is electronic

ANSWER: Hi P.  You should have a Lucas 45DE4 distributor.  It has a circular vacuum module that appears to be blanked off.  However, there is a vacuum pipe attached to the other side of the vacuum module.  Have a closer look.  If it doesn't have one, I need to see a photograph of your setup.

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QUESTION: Where would you like me to send the pic ??
I have it out and mostly apart the wing on the advance are frozen and it has optical sensor and pick up if this helps
Lucas part # 41643B 43DE4  14/6 england pat

Answer
You have given me Lucas part number 43DE4.  That is all I need to know.  These are known as Lucas OPUS distributors.  Here is an exploded diagram of one:

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29064

The vacuum unit is part #7.  There should be a small vacuum pipe attached to it, the other end attaching to the carburetter.  If the vacuum unit is faulty or missing, that would explain your troubles.