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advance/retard checking

Posted: Fri Mar 22, 2019 7:49 pm
by PeterSE6a
Hi I have timed my 6a with a stroboscope , is there a way of checking with the strobe the vacuum advance retard and the bob weight advance retard . When I checked the timing the light point moved to the left when I revved the engine , then settled back to the proper strobe mark on tick over , was that the vacuum advance/retard ? The strobe method was as described in the RSSOC special Workshop Manual , thanks . :D

advance/retard checking

Posted: Fri Mar 22, 2019 8:54 pm
by rebel alliance
I'm guessing but if you removed the vacuum pipe would you only get the bob weight advance degrees...

advance/retard checking

Posted: Fri Mar 22, 2019 8:59 pm
by Old and Slow
Also, the vacuum tends to be active when the throttle closes (on over-run etc, to advance the ignition when the mixture is rich and takes longer to burn - helps stop the popping and banging); when the throttle is open wide there's very little vacuum.
Therefore if you open the throttle to increase the revs, as Rebel Alliance says, you are mostly seeing the effects of the bob-weights.

advance/retard checking

Posted: Sat Mar 23, 2019 7:41 pm
by Roger Pennington
As has been said, with the vacuum pipe disconnected and plugged, you should only see centrifugal advance when you rev the engine, and you can then check it against the book figures.
If you have access to a Mityvac (or similar) vacuum tester/brake bleeder, (with a gauge), then you can connect it to the vacuum advance capsule on the dizzy and apply specific amounts of vacuum, and see if the amount of advance that you get corresponds to the vacuum advance curve in the book.