Don---Can you describe what happens visually with the rotor(s) that
needed replacing? Can you see scuffing, like the rotor tip came into
contact with the cap tower terminals?
I've been using Lucas rotors and caps for years without the need to
replace them move often than say, every 50,000 miles or more. I also use
the MSD6A (no rev limiting feature) and I can't see any reason for this
to contribute to rotor failure in and of itself.
The rotor shoud be snug on the end of the distributor shaft, so there's
no way it can wobble or rise upward to clash with the cap during
operation. The rotor should also be of the proper length to come close
to, but not contact the cap terminals. You can wipe the brass edge of
the rotor with a marking pen to check to be sure no such contact takes
place, as might happen, say from a very sloppy distributor shaft. Of
course there should be evidence of contact inside the cap itself.
If your distributor shaft happens to be suspect, this should show up as
a large variation in ignition timing, and picked up with a light, at
road speed rpms.
I would start with a good set of Lucas cap and rotor. They're designed
to work together. (I've seen TR's with some really bad combinations come
my way.)
Please let us know what you find.
Dick T.
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