There is one other possible problem not mentioned in previous posts that
might give similar symptoms. The fiber timing gear will sometimes fail over
a period of time, especially when coming loose from the knurled steel hub.
In my experience it happens like this:
You wind it up pretty hard and when you get to about 4500 rpm or so it is like
you suddenly turned off the switch. You step on the clutch and roll to a stop
and find it is idling perfectly. This happens several more times at
successively lower speeds, and then it just quits, won't start, fire or
anything. Usually you'll hear a significant knocking from the timing cover
(although it is hard to tell exactly where it is coming from) before it
finally completely lets go. When it is starting to fail you can tell because
with a timing light, at steady or slightly varying speed the timing will vary
more than you would expect. When it does let go completely you can tell because
the distributor doesn't turn when you crank the engine.
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George Downs, Bartlesville, Oklahoma, Central US