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Old 11-03-2011, 09:23 PM   #6
Marco Tahtaras
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Join Date: May 2010
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Default Re: Spark advance or Spark retard

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Modern vehicles have an automatic advance relative to speed and other conditions. Generally, the greater the engine RPM the greater the advance.

Now most Model A owners don't feel the strains which are very similar to needing to down shift. They simply start the car, fully advance the spark. and go driving. I decent Model A with stock compression will survive this just fine most of the time ON FLAT GROUND. Putting it under a load such as towing something or climbing a hill makes the timing relative to engine speed more important.

With additional compression (high compression head) it becomes even more critical for two reasons. First, the increased pressure places additional stresses on the lower end. Second, higher compression increases the burn rate of combustion. That means it responds quicker to the firing of the spark plug which in essence means it advances the timing somewhat all by itself, so you must compensate slightly with the spark lever.
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