Buoymaker and Jon,
Thank you, Jon especially for the advice.
Dwell was off - point gap was over .018". I didn't check timing before adjusting gap, so I can't confirm how far off it was before adjustment. Timing was a couple of degrees retarded after the dwell re-set and warm-up.
Gap has been re-set and the timing re-adjusted, slightly advanced as suggested. The test drive went well - the part-load response is improved. I'll keep an eye on the plugs after I get a few more miles on and see if that improves the situation.
Thank you again,
Bill
