No, as long as the idle is where it should be.
(in drive the idle is usually lower than in Park)
If it is set at full advance, it would just be to check what it is at idle.
If you watch the timing mark when it is revved up, it should move nicely not in a jerky motion.
(and it should move quite a bit)
As others said, plug the vacuum line because it will make the engine idle faster usually.
(if doing it at idle)
FYI, A lot of the timing lights that have the adjustable timing knob are not very accurate.
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John Wallace - johnta1
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