No guru here, but I've seen a loose backing plate screw show the same
symptoms. You don't notice it at rest when setting the points, but under
load allows the gap to change.
Took an hour or so by the side of the road to figure that one out!
> Points. Yuck. I'm so glad I went to electronic ignition on the
> rally car ('68 'B GT). Prior to that wonderful move,
> (well wonderful except when I got hit by an ignition spark!
> wow!) I had a strange thing going on that at first
> I could not explain, then, like so many bizarre car situations,
> it seemed totally logical when I found the progenitor
> The car started to run poorly, symptoms of an ignition fault. It
> had fairly new wires, plugs, cap, rotor, points, condenser...
> I checked the points gap. Way too small. Adjusted it, drove
> car. Ran OK for a while, then back to classic
> ignition fault behaviour...
> I could NOT keep my points adjusted. I'd set 'em, the car
> would run great for a trip or two around the block, and then
> start to stumble again....
> I'm not going to tell you what I found right away, here's a
> chance for the gurus to do some "bench wrenching".
> -Keith Wheeler
> Team Sanctuary