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Old 09-24-2017, 10:42 AM   #5
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Join Date: May 2010
Posts: 3,917
Default Re: Distributor vacuum brake question

My chart from a old Ford training guide says :

Governor weights spread as speed increases thereby advancing spark.
The same vacuum force that operates your windshield wipers also retards the ignition spark.

As i run one of these almost every day on a machine. I would explain it like this:

Engine off leather brake holds the advance ring by spring tension causing a slight retard in timing allowing a easier start.

Once the engine starts vacuum pulls brake off the advance ring allowing a proper advance as soon as the engine starts.

Driving down the road and hitting a hill (increase load) vacuum will drop off causing a retard to timing preventing spark knock.

There are some good pictures on our web site

I guess its how you word it?????
If it Makes Spark, we do it !!!!
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