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Hi Ron;
In a perfect world yes, but the problem is that if the advance curve is lazy, or fast because of a weak spring or two, the pinging one encounters up to about 3500 crank rpm may cause one to either over or under advance the timing at rpm's above that by changing the intial setting. If a spring is weak or broken, and the timing set to avoid ping, then the total advance is low, and conversely if the upper shaft of the distributor is seized, then huge intial advance is set, and still the total advance is low.
I had a customer who once explained that the timing on his engine was best at 21 degrees at idle. That didn't make sense. I checked and the upper shaft was siezed. I loosened everything up, and set the intial to about 12, but had 35 total at 3800 or so. Engine ran like gangbusters.
To the other posts regarding carbon and it's effect on compression ratio, leaded fuels in the old days could cause well in excess of a quarter point or even a half point increase simply through the large deposits leaded fuels produced. More importantly though is the fact that carbon is a poor conductor of heat, and will retain enough heat to produce self-ignition, during the last phase of the compression stroke, and cause pinging unrelated to the spark point. Any engine rebuilt after the advent of unleaded fuels won't have this problem, but an original one may still have carbon deposits capable of doing this.
Timing lights are best used to check the advance curve as the engine rpm is increased. Using one to simply set intial advance limits their worth. Using a total advance nearing 40 degrees on a pushrod redblock can produce inaudible detonation, and that's going to end in tears.
Modern engine management systems are so incredible compared to these old systems - and much of what they do is vary ignition timing with load and fuel ratio all the way to redline.
Rhys
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