I have a manual for my 1980 MGB. After reading about the setting for
the spark advance, it gave me little useful information.
A MGB owner told me that the engine running at 1500 RPM should have
about 11 degree before TDC. The car had about 20 to 25 degrees
before TDC. The vacuum advance should be off at that time. He then
said the vacuum should be reconnected and an increase of about 20
degrees above the 11 degrees should occur. That did happen. When I
sucked on the advance vacuum the engine increased RPM.
Question
1. Is the correct procedure?
2. Why did the RPM increase when the vacuum was advanced?
3. The vacuum advance line goes from the intake manifold to a
box on the brake housing then to the spark advance. I was told it
open the vacuum to the spark when the switch was turned on. Why is
it not on all the time? Is there a reason for this?
4. Is there a correct procedure?
Thomas L. Burgin
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