<VV> Re: points, dwell, steady timing

[djtcz@comcast.net]

> To get the dwell in the 30 thru 33 range the points have to be set        > at .009 or .010. All the vacuum hoses have been replaced, could a      > worn distributor be the cause of the small point gap?
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As far as gap and dwell not matching specs, one unlikley way would be for the lobes on distrib's points cam to have simply worn down.  I suppose if the point's rubbing block was BADLY worn,  it would present a broad surface, the corner of which would hit the opening ramp sooner than the desired center point. The other corner would leave the closing ramp later, reducing total points closed dwell, even if the gap was set correctly,.
My experience with some points distributors with worn bushings has been the timing is even more unsteady than usual.  My very questionable recollection is that even on a poorly running car with very worn bushings (the rotor had touched some of the cap contacts) the dwell readings were not that unsteady. I suspect heavy dwell instrument damping simply hides some the variation.  Looking at the signal with an oscilloscope would show the true picture. When I checked the timing on my Dad's first car with electronic ignition I remember being in AWE  of the steady timing marks. If the timing light shows the timing is jumping around (varying 5 degrees, sometimes WAY more) at a steady low engine speed, I figure it could misbehave at least as bad when revving up and down.  I think that steady ignition timing is a BIG advantage, and only attainable with magnetic or optical triggering.  My friend had a vicious 400 cc racing dirt bike with fixed timing via crank mounted points. It also had worn main bearings that allowed detectable radial crank (and points cam) looseness.  We carefully tuned it to produce a beautiful blue spark and precise point gap and accurate static "points open" timing. But it was a stubborn misery for powerful young men to kick start.  Kickety-kickety-kickety-kick.  The day a magnetically triggered ignition was installed it became a 2 kick starter. I believe that was because the dynamic ignition timing was finally close to the factory's real intended value.  On any points system the shaft clearances allows the point gap to vary instantaneously, and that's why the timing varies.  It's easy to get a points distributor positioned near the desired timing point so that gentle sideway pressure on the rotor can make a spark.
I love points because they can almost always be "fixed" on the side of the road.  I hate points they have to be.