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MGB Vacuum advance and Electronic ignition conversion

The Green Hawk

Freshman Member
Hello all, New member here!

I have a 1980 MGB that has the Weber DGV conversion and an electronic ignition. I have a question about vacuum advance.

I just discovered the vacuum advance diaphragm is bad, verified by the oral suction test. My question is about the need or use of vacuum advance with a modified distributor.

Is the vacuum advance still needed?? My own logics says YES, but have read several posts stating the opposite.

Also, just read the "White paper" and what a great source of hard to find information. One topic that was particularly helpful was valve lash adjustment using the Rule of Nine method.
I had gone through the RoN method twice which resulted in horribly ratty sounding valves each time. In the process, I discovered that the maximum amount of gap was not as stated in the RoN method.
I moved the crank forward a few degrees at each valve and found that the gap on valves 2,3-6,7 were wider at a few degrees beyond what the method stated. As it turned out I simply used the RoN to get close and then found the widest gap manually by moving the crank a few degrees. This worked wonderfully!!! I'm not sure why this is, but for now it works great.

Also you may have noticed that the valves I referenced were all INTAKE valves!! Again, not sure what to make of this and would very much like to hear if anyone has some ideas!!

The Green Hawk


Mine is bad as well, never replaced the vacuum unit on a distributor but it's probably not too difficult right?
Jeff S. says they go bad pretty quick with manifold vacuum being used, that's what I've got.

The Green Hawk

Freshman Member
Thanks trumpetman!!

I have visited the distributordoctor website before and have added them to my list of useful resources!

Also, I checked out the mgpartsuk website and glad to have an alternative to Moss. Pricing appears a lot better than Moss as well.

The Green Hawk

Freshman Member

I think your right that replacing a bad vacuum advance unit is not that hard. The concern I have is finding the CORRECT replacement unit.
I have heard that they are NOT all created equal.

I found a great resource about CEI distributor. they show a way to repair a failed vacuum advance!

am learning that it was only offered originally, on the 1980 but appears to be retro-fitted to several other years.




Thank you, that's an interesting article and I've only just started reading.
I'd rather find a good vacuum unit to buy but like you don't want to get burned.
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