when is the "F" mark referenced?
As 5thinline wrote, the "F" mark is the static timing - essentially, where the timing light should shine at idle. When you are starting from scratch, you set the crankshaft to "F", and rotate the distributor CCW until #1 fires - that gets you close enough to start the engine.
But the odds are low that your distributor's range of advance will exactly hit "F" at idle and "M" at maximum RPM. And the maximum setting is more important. So as you wrote, you set the timing to "M" at 5,000 rpm, and let the idle setting fall where it will.
(Copied from earlier thread)
It always is exciting to run the car at 5000 and look for M with the fan blades whirring in your face.
Last edited by Dr.G; 01-13-2017 at 08:46 AM.